i have a few low hugel beds in my gardens, mostly were filled with branches or bark or woodchips as they were available..but they were DUG first, soil removed, area filled with woody material and
compost and then refilled with the soil that had been removed from the holes..they never got more than a couple of feet high, but they worked out very well..some have
apple trees planted on top of them..and they are doing quite well (only been 2 years)..
I am going to be removing some jerusalem artichokes that are running along one side of several of my beds also this year, moving them. And so there will be ditches and removed soil when the JA's are removed, I plan to fill those ditches with woody materials and then refilling them with the soil on top also..this kinda has become a way of life for me when I redo a bed ..and it has worked out pretty good..just doing it a little at a time (being 61, a woman, partially disabled and no real help)