Has anyone tried making this with gluten free flour?

I have not made this particular "Chocolate Dump-It" cake using a GF flour blend, but I have had uniform success in cakes like this substituting the gluten-free mix sold by King Arthur Baking, which is called "measure for measure." It's easy to use, and I've never had any issue, ever, with its performance.

Incidentally, I buy the product at our local Target - which means I don't need to order it from King Arthur Baking. Their price is quite reasonable compared to every other grocery store in town that carries it.

Hope this helps! ;o)