Does polenta freeze well?
Sounds like you want to pop frozen slices into a frying pan? That should work just fine. The slicing allows for quick freezing, which decreases the size of water crystals and the effect they have on food. And quick frying keeps the disturbance of the polenta to a minimum.

In general, basic polenta should be fine, since starch, the many component to consider, responds alright to freezing. Recipes with cream make things more complicated. Freezing and reheating cream can lead to separation, so reheating a big block in a pan could leave you with pools of oil.