diff --git a/plugins/woocommerce-blocks/src/BlockTypes/ProductQuery.php b/plugins/woocommerce-blocks/src/BlockTypes/ProductQuery.php
index f7dff2df89d..4ba07717b56 100644
--- a/plugins/woocommerce-blocks/src/BlockTypes/ProductQuery.php
+++ b/plugins/woocommerce-blocks/src/BlockTypes/ProductQuery.php
@@ -48,6 +48,13 @@ class ProductQuery extends AbstractBlock {
 	 */
 	protected $is_custom_inherit_global_query_implementation_enabled = false;
 
+	/**
+	 * All query args from WP_Query.
+	 *
+	 * @var array
+	 */
+	protected $valid_query_vars;
+
 	/**
 	 * Initialize this block type.
 	 *
@@ -186,42 +193,17 @@ class ProductQuery extends AbstractBlock {
 	 * @return array
 	 */
 	private function merge_queries( ...$queries ) {
-		$valid_query_vars = array_keys( ( new WP_Query() )->fill_query_vars( array() ) );
-		$valid_query_vars = array_merge(
-			$valid_query_vars,
-			// fill_query_vars doesn't include these vars so we need to add them manually.
-			array(
-				'date_query',
-				'exact',
-				'ignore_sticky_posts',
-				'lazy_load_term_meta',
-				'meta_compare_key',
-				'meta_compare',
-				'meta_query',
-				'meta_type_key',
-				'meta_type',
-				'nopaging',
-				'offset',
-				'order',
-				'orderby',
-				'page',
-				'post_type',
-				'posts_per_page',
-				'suppress_filters',
-				'tax_query',
-			)
-		);
-
 		$merged_query = array_reduce(
 			$queries,
-			function( $acc, $query ) use ( $valid_query_vars ) {
+			function( $acc, $query ) {
 				if ( ! is_array( $query ) ) {
 					return $acc;
 				}
-				if ( empty( array_intersect( $valid_query_vars, array_keys( $query ) ) ) ) {
+				// If the $query doesn't contain any valid query keys, we unpack/spread it then merge.
+				if ( empty( array_intersect( $this->get_valid_query_vars(), array_keys( $query ) ) ) ) {
 					return $this->merge_queries( $acc, ...array_values( $query ) );
 				}
-				return array_merge_recursive( $acc, $query );
+				return $this->array_merge_recursive_replace_non_array_properties( $acc, $query );
 			},
 			array()
 		);
@@ -450,9 +432,11 @@ class ProductQuery extends AbstractBlock {
 
 		return array(
 			'meta_query' => array(
-				'relation' => 'AND',
-				$max_price_query,
-				$min_price_query,
+				array(
+					'relation' => 'AND',
+					$max_price_query,
+					$min_price_query,
+				),
 			),
 		);
 	}
@@ -499,8 +483,10 @@ class ProductQuery extends AbstractBlock {
 
 		return array(
 			'tax_query' => array(
-				'relation' => 'AND',
-				$queries,
+				array(
+					'relation' => 'AND',
+					$queries,
+				),
 			),
 		);
 	}
@@ -542,6 +528,112 @@ class ProductQuery extends AbstractBlock {
 		);
 	}
 
+	/**
+	 * Return or initialize $valid_query_vars.
+	 *
+	 * @return array
+	 */
+	private function get_valid_query_vars() {
+		if ( ! empty( $this->valid_query_vars ) ) {
+			return $this->valid_query_vars;
+		}
+
+		$valid_query_vars       = array_keys( ( new WP_Query() )->fill_query_vars( array() ) );
+		$this->valid_query_vars = array_merge(
+			$valid_query_vars,
+			// fill_query_vars doesn't include these vars so we need to add them manually.
+			array(
+				'date_query',
+				'exact',
+				'ignore_sticky_posts',
+				'lazy_load_term_meta',
+				'meta_compare_key',
+				'meta_compare',
+				'meta_query',
+				'meta_type_key',
+				'meta_type',
+				'nopaging',
+				'offset',
+				'order',
+				'orderby',
+				'page',
+				'post_type',
+				'posts_per_page',
+				'suppress_filters',
+				'tax_query',
+			)
+		);
+
+		return $this->valid_query_vars;
+	}
+
+	/**
+	 * Merge two array recursively but replace the non-array values instead of
+	 * merging them. The merging strategy:
+	 *
+	 * - If keys from merge array doesn't exist in the base array, create them.
+	 * - For array items with numeric keys, we merge them as normal.
+	 * - For array items with string keys:
+	 *
+	 *   - If the value isn't array, we'll use the value comming from the merge array.
+	 *     $base = ['orderby' => 'date']
+	 *     $new  = ['orderby' => 'meta_value_num']
+	 *     Result: ['orderby' => 'meta_value_num']
+	 *
+	 *   - If the value is array, we'll use recursion to merge each key.
+	 *     $base = ['meta_query' => [
+	 *       [
+	 *         'key'     => '_stock_status',
+	 *         'compare' => 'IN'
+	 *         'value'   =>  ['instock', 'onbackorder']
+	 *       ]
+	 *     ]]
+	 *     $new  = ['meta_query' => [
+	 *       [
+	 *         'relation' => 'AND',
+	 *         [...<max_price_query>],
+	 *         [...<min_price_query>],
+	 *       ]
+	 *     ]]
+	 *     Result: ['meta_query' => [
+	 *       [
+	 *         'key'     => '_stock_status',
+	 *         'compare' => 'IN'
+	 *         'value'   =>  ['instock', 'onbackorder']
+	 *       ],
+	 *       [
+	 *         'relation' => 'AND',
+	 *         [...<max_price_query>],
+	 *         [...<min_price_query>],
+	 *       ]
+	 *     ]]
+	 *
+	 *     $base = ['post__in' => [1, 2, 3, 4, 5]]
+	 *     $new  = ['post__in' => [3, 4, 5, 6, 7]]
+	 *     Result: ['post__in' => [1, 2, 3, 4, 5, 3, 4, 5, 6, 7]]
+	 *
+	 * @param array $base First array.
+	 * @param array $new  Second array.
+	 */
+	private function array_merge_recursive_replace_non_array_properties( $base, $new ) {
+		foreach ( $new as $key => $value ) {
+			if ( is_numeric( $key ) ) {
+				$base[] = $value;
+			} else {
+				if ( is_array( $value ) ) {
+					if ( ! isset( $base[ $key ] ) ) {
+						$base[ $key ] = array();
+					}
+					$base[ $key ] = $this->array_merge_recursive_replace_non_array_properties( $base[ $key ], $value );
+				} else {
+					$base[ $key ] = $value;
+				}
+			}
+		}
+
+		return $base;
+	}
+
 	/**
 	 * Get product-related query variables from the global query.
 	 *
@@ -582,3 +674,4 @@ class ProductQuery extends AbstractBlock {
 	}
 
 }
+