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.
Mounting a sub panel to a concrete basement wall.
Very low water table area.
If it s my choice i ll mount a panel directly to a concrete or block wall.
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.
And the shorter distance between the two panel means a cheaper installation.
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.
Then remove the tape.
Since the sub panel is only 14 wide i will still have at least 3 of space between it and the main panel as well as between it and the adjacent wall.
If the back of the panel was flat i d definitely use plywood.
I am showing a cheap trick when you don t want to spend the money on expensive dowels or specialized mounting devices.
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.
Just a drill and a piece of wood will.
Normal placement of your new sub panel will be down in the basement directly beside the existing electric panel.
Only 1 8 or so but it keeps the moisture out.