Where have my iris mounds gone?

I have been planting iris on raised mounded rows for drainage, but realized just today that the ground has leveled out, hiding the rhizomes...I also see that the big clumps are way too crowded; the ones that survive grow fast. I am thinking that there needs to be at least 2 feet of mound around the end of each clump, not from the center of one clump to the center of another clump. This means a whole lotta dirt cleared and kept weed free...What do you think about using flat rocks down a mound to keep the roots buried and mulched, while keeping the top of the rhizome exposed at the top of the clump? Also this would mean relocating each baby plant as it grows bigger and needs a higher mound to keep it above ground. Would you think that after each new iris blooms for the first time it could be relocated intact to a more spacious and taller mound? I am just not going to start out with each baby rhizome 4 feet apart...