How can I make the time selection to use drop-downs instead of sliders?

This is done via a WordPress filter. You can find this and other possible modifications described under the “Developer’s Information” section on the product page, together with examples and a link to a tutorial.

In this case, the PHP code snippet involved is:

add_filter('openinghours_timepickercontroltype', 'my_openinghours_timepickercontroltype');
function my_openinghours_timepickercontroltype($t) { return 'select';}

Posted in: WooCommerce Opening Hours and Delivery Times