I've started construction of my wood-burning oven. Right now I'm kind of in the test phase. I put the fire pit together (which in the instructions specifically says it's not for grilling or other cooking purposes) and attempted my first mixture of perlite and portland cement at about 3:1 perlite to cement by volume. Hopefully this will set well and make for a relatively solid block.
I really have no idea how much water to add to the mix. There doesn't seem to be a standard ratio for that. I may have made it too soupy to set properly...The good news is that the perlite makes for an ultra light mixture, so making it easy to move and store shouldn't be a problem.
If anyone reading this has any knowledge they'd like to drop regarding masonry or oven building, please speak up.