Ground Preparation/Tree Removal

[dis_250]

I had to remove a small tree from the area where we want to put the pool.
A hole in the ground is about 25"x40" and 11 inches deep.
What is the best way to fill it?
I would like to avoid excavating 11" to level the whole area.

Backyard is all fenced and I can not get in any big machinery.
I’m located in Toronto area, Ontario Canada.

AG 15x25

Thanks,
Dusan