Would using frozen sweet potato slices work in this recipe or would they be too mushy?

Thanks for the speedy reply. I had already gone ahead and used them and, in fact, they turned out great. I’d frozen them raw, let them thaw almost all the way before putting them in the muffin tin. Note that they needed about ten minutes less cooking time but still turned out crisp around the edges. As the recipe called for, I left the foil cover on for 20 minutes, but then cut the cooking time after removing the foil cover to about 10 to 15 minutes.

you cheated! you never said anything about freezing them raw!

Oh! Apologies for omitting that key detail. It was a case of having sliced too many sweet potatoes for another dish, and stashing the unused portion in the freezer.