How do I keep my Calzones from getting soggy on the bottom after baking?

Bake on parchment paper.

OR

Put some cornmeal down and bake the calzones on a light coating of cornmeal. Cornmeal will act like little ball-barrings and make it easy to remove the calzone.

Once you remove the calzone place on a wire rack to cool a bit. The rack will prevent moisture from collecting under the calzone.

You could use an ovenproof rack to cook them on. The rack will help the airflow around the cal zones, hopefully crisping the bottoms or turn them once one side starts to brown. Try lining your baking sheet/pan with Reynolds non-stick aluminum foil or parchment paper to avoid sticking.

Lightly grease the sheet and place them on a wire rack as soon as they are done. Or use parchment paper.