3 letters:
kol, rol

4 letters:
boal, bohl, bole, boll, bowl, buol, coal, cole, dole, foal, fohl, goal, gohl, hoel, hohl, hole, kohl, kole, mohl, mole, nohl, nole, noll, pohl, pole, poll, rohl, role, roll, sohl, sole, soul, thal, thul, toal, tole, toll, wohl

5 letters:
boehl, coale, colle, dhole, doell, foale, hoell, knoll, koehl, noell, pfohl, poehl, roehl, roell, rolle, seoul, sowle, thall, theel, theil, thiel, thill, thobe, thode, thoen, tholl, thome, thone, thull, voell, whole, woehl, thole

6 letters:
hoelle, knoell, koelle, roelle, schaul, theall, theile, thiele, toelle

7 letters:
scholle