I've had mixed success keeping very, very easy plants in pool filter sand with a very course grain. I only keep anubias, java fern, and crypts (and java moss, but that's all on the driftwood). For the anubias and java fern, I just poked some of the roots down into the sand and let some stay above the substrate. The crypts' roots are completely below the sand.
After a few months, the java fern is breaking apart and turning very dark and not really growing all that well (it was an experiment anyway), I've had some trouble with yellow and curling leaves on the anubias, but the ones that have 3 or 4 root ends poking up above the sand are doing well, and the crypts are doing absolutely fantastic. Bear in mind that I am running less than 1 wpg on my tank as well. LOL Super low-tech.