Welcome to this National Gardening Association forum. It will help to identify the culprit that is eating your hollyhock seedlings. Glance at them frequently during the day and go out with a flashlight to inspect them at night. Slugs and snails tend to feed at night. If it is slugs, sprinkle a bait called Sluggo around. They will eat it preferentially and die.
If it is not slugs or snails, you might consider making some kind of protective barrier to keep the leaf eaters away. Or spray your hollyhocks with a systemic insecticide. I have on occasions protected individual zinnia blooms with "hairnets" made from a fabric I found at a fabric store.
That first zinnia plant is protected by nylon screening material attached (sort of) to a "zinnia cage". The individual bloom is protected by a special fabric. There is a name for that kind of fabric, but I can't think of it at the moment. In any case, if you put your thinking cap on you might be able to think of some way to protect your hollyhock plants from whatever is eating them.