woocommerce/plugins/woocommerce-blocks/assets/js/base/components/checkbox-control/style.scss

.wc-block-checkbox {
	display: block;
	position: relative;

	.wc-block-checkbox__input[type="checkbox"] {
		appearance: none;
		border: 1px solid currentColor;
		height: 1rem;
		margin: 0;
		min-height: 16px;
		min-width: 16px;
		overflow: hidden;
		position: static;
		vertical-align: middle;
		width: 1rem;

		&:checked {
			background: currentColor;
			border-color: currentColor;

			&::before {
				color: #fff;
				content: "\2713";
				display: block;
				height: calc(1rem - 2px);
				min-height: 14px;
				min-width: 14px;
				margin: 0;
				line-height: 100%;
				text-align: center;
				width: calc(1rem - 2px);
			}
		}
	}

	.wc-block-checkbox__input[type="checkbox"] + .wc-block-checkbox__label {
		padding-left: $gap-smaller;
		vertical-align: middle;
	}
}