I can't find the webpage now! Of course, it was years and years ago.

I do have it printed out..somewhere. There was probably 20 different 'clay' recipes on there.
I seem to remember that it was one cup of flour, one cup of coffee grounds, 1/2 cup of salt and enough water to mix into a clay. I know I used damp coffee grounds, so I didn't have to use as much water. Seems like the second time I made it, I used a little coffee instead of the water.
You might have to use more flour as that's the binding agent. The finished projects are air dried and look like stone. They should dry hard and not crumble. Most of mine were just cut out with a cookie cutter into basic shapes. I used whole cloves. bits from old potpourri, little cinnamon sticks, tiny dried flowers, odds and ends, etc on my ornaments, using a cool melt glue gun.
Even the recipes for homemade playdoh can be a great medium to work with and the projects don't have to be flat as they hold their shape fairly well. I made literally dozens of roses, leaves. I tinted the leaf mixture with green food coloring as used them as is. The roses were painted with old nail polishes after they dried. I loved the pearl colored ones. Some I would paint the edges of the petals with a red shade, then go over the whole flower with a pearl. I still have some of them, they must be at least 15 years old by now.
The drier lint clay looks like light blue denim (I made little baskets, put in a foam block, glued on moss and old potpourri flowers).
I'm a pretty good 'trash' artist. My favorites are a couple of wooden boxes covered with onion skins (the papery part on the outsides of the onions) and one box that has an egg shell mosaic. That one took for-e-ver to do.