If it s my choice i ll mount a panel directly to a concrete or block wall.
Mounting a sub panel to a concrete basement wall.
This just makes sense because you connecting the sub panel directly into the existing panel.
As stated above most if not all panels have dimples in the back of the can to provide a bit of space from the wall.
I am showing a cheap trick when you don t want to spend the money on expensive dowels or specialized mounting devices.
Only 1 8 or so but it keeps the moisture out.
As an alternative i could always mount the sub panel on the adjacent wall so that it s facing 90 degrees to the main panel.
I usually use tapcons.
Then remove the tape.
Normal placement of your new sub panel will be down in the basement directly beside the existing electric panel.
Just a drill and a piece of wood will.
The basement is finished but foundation walls are bare concrete electrical stuff is surface ac cable when it needs to provide outlets and devices on foundation wall.
Tape a one foot by one foot square of plastic sheeting plastic kitchen wrap will do to the concrete wall in your basement with duct tape and leave it in place for 24 hours.
If the back of the panel was flat i d definitely use plywood.
Very low water table area.