On a welding forge, the floor should be a highly flux resistant material, like bubble alumina.
This search engine will get you dozens of threads with great info (as well as the info in the stickies).
https://cse.google.com/cse/home?cx=011197018607028182644:qfobr3dlcra
Just a question for clarification - Are you welding up damascus in your current small forge?
Some basic info:
Two layers of 1" Hi-Z inswool, or one 2" layer of regular inswool, are best for a welding forge ( or any forge). The Hi-Z wool is better if you are working at welding temps.
A 1/4-3/8" layer of Satanite ( over the inswool) with a final coating of ITC-100 will give great performance and long life. Fire and cure the satanite before applying and curing the ITC-100.
In any welding forge, have a floor that is either replaceable ( kiln shelving), or made from a flux resistant material like Bubble Alumina.
High Temp Tools is the place for all your forge building stuff. They have everything from wool to ITC-100 -
www.hightemptools.com
Insboard makes great forge ends and floor material.
Make it big enough, but not excessively. A 10"X16" pipe makes a great forge. The final chamber will be about 6"X14"
A vertical forge is really good for welding damascus. Put 2" of kitty litter in the bottom to catch the flux.