Thanks - A natural stone look was what i was after - and it came out pretty nice. I used the pink styrofoam from home depot ( insulation board ) and glued multiple pieces together ( found out that the best glue was a hot glue gun with low temp glue sticks from a craft store ) I just rough cut pieces with a razor knife to create the main shape your after and glued them together - then I took a dremel with a sanding drum and went to town carving it - trying not to make it flat and smooth instead add gouges and crevices to shape it like real rock . Then I blew the dust off and I used non sanded grout in a color you want to show in the ridges - mixed thin and applied it with a paint brush - let dry and apply again - maybe a little thicker - let dry - and then I used sanded grout in the main color you want and again mix fairly thin and apply with a paint brush , after it dryed a short time I took a wet sponge and lightly wiped off the sanded grout on some of the ridges to expose the other color - let dry and do it again , mixing it thicker - let dry and wipe again till you get the multi color effect that looks natural and that you like . You can put on as many coats of each as you like - I would recommend at least to of each. or add more colors of you choose . after your happy with the colors it's time to let it dry well - and then seal it - I used shellac ( because it's hypo allergenic and food safe )applied with a brush and did 3 coats , make sure you let dry until the smell of the shellac is gone - maybe a day ? - what I found out - is that the grout and sealer continue to harden for a long time - and to begin with it is fairly brittle - so be very gentle with it if you are installing it right away as you can chip it fairly easy . also if I where to do it again - I would not make it removable -I would glue it and grout/seal the edges all tight so the bugs your feeding your buddy , can't get behind it and hide . let me know if I can help further - good luck