Thats a great way to practice...... I wish I had a place to practice from an elevated position.... but I do not. What I do try to do is simple.
I - before work, and after shoot one arrow - at 40 yards... sometimes 30. And I do all I can to hit a bullseye.... I concentrate - on ONE SHOT.... I have found that doing this really increases your concentration.... my goal is 7 10 rings at the end of a week.......
I still practice groups at 40 and 30, and a few 15-20 yard shots...... but I mainly practice at 40... this makes 20-30 yard shots seem quite easy after you have shot 100' s of arrows at 40.......

Thats it

Good luck, and dont loosen that soil too much !!