1 layer of Vinyl for top
2 layers of flleece for padding
1 layer of some fuzzy upholstery material, closest to tank
1 Roll of leather lacing for edge
Make a cardboard pattern (looks like a coffin with a hole for your gas cap) transfer to material; sew all layers together following the pattern. Cut bib from excess material. Punch holes along the edge, use leather lacing around the edge keeping the lacing flat.
It was pretty simple to make. My tank has been repainted so I'm not worried about the scratches it might make although everything is soft on the bottom. I think I spent about $10 at the fabric store on remnants and the lacing.