The first fitting is not bad, the backer board needs a bit of trimming, maybe a mm or two off where the angle meets the forward vertical and I expect after looking at the left forward peg and mortise I'll drill the mortise a couple or three turns deeper.
I'll piddle with the fitting a little then clean up and flatten the slab and trim the ends. After the slab clean up I'll round the ends of the long stretchers and mount the chop followed by making the tool tray.
Making a tool tray can be a PITA because it is so long but bottom line it is not structural and almost any joint is strong enough. The biggest problem is finding or making boards that are long enough and straight enough to use.
This sucker is almost finished, in fact if needed it could be used as a bench today.