You need one layer of fleece as it has to be touching sometime absorbent underneath to get the drawing away of pee process going. If you have two layers of fleece the top layer will be touching fleece which wont draw the wee downwards, if that makes sense! Did you mean two layers of fleece, if not ignore that bit!
I use two layers of towels, tea towels or mattress protectors - its pretty much what I had in the box of rags! I found that one layer of good thick towel will work on its own or two layers of thinner towel. Experiment around and if you use newspaper check to see if there are any stains, if there are then add another layer! Good luck and post some piccys of the finished result!