Destruction and redo!

[OLS]

Might just split a 5 gallon bucket that's had the bottom taken out and use half on either side and back fill?
There are solutions out there, I just know that arborists tell you to never mulch up a trunk, to use no mulch at
the trunk and a sloping pile outward, kind of like an ant lion pit. There is a solution somewhere in a pile
of junk, you just have to find it.