I followed these directions last year and use the foam table on top of an Ikea sewing desk (actually, it was a computer desk). But, instead of the clear vinyl, I used white oilcloth...the modern heavy-weight stuff. It is very slick and you can't see the foam through it. It's been perfect for quilting. I ordered the oilcloth from Mendels.com; they have a huge selection.
One thing I have had a little trouble with is the back edge of the opening for the presser foot plate that you cut in the vinyl/oilcoth. Sometimes the edge of a piece of fabric will get caught on that edge. I taped it down with blue painters tape but you need to replace the time from time to time. Not a big deal at all. I love my table.