Demo of bundle product. There are 3 items (canvas tote, burlap tote, and enamel mug) and customers do not get an option pick what goes in the bundle. All 3 items are always included.
This product uses 3 pick lists. Each pick list has a single item, set as the default selection, that is required for checkout. I've added {{#contains display_name 'Bundle item'}} style="display:none" {{/contains}} in one of my template files to hide the pick lists from the PDP so as not to confuse customers.