You can cut the from or back first. I have duplicated the internal cut out on both files so yo can choose which to cut first.
Cut the front/back and flip over and cut the back recess. Cut the insert (from 4mm material/hardboard) and this will then sit snugly into the recess to give a flush finish.
Sand and Oil as required.
Add fixings to hold insert and to hang (extras and not included).
A good intermediate project due to the flip but again only requiring two bits.