I think you ar right to cut the miter and the bevel first. Yes typical
ox joint jig with with following modifications.

1. Tilted blade

OK, but if you tilt the blade, the blade height will have to be
adjusted for each cut, because the workpiece will only touch the table
at one point. Also, the tilted geometry will complicate the spacing.

2. the back fence needs to tilt back at the same angle as the end
bevel (22.5?) so the joining face of the miter cuts ar flush to the
table suface of the jig.

I respectfully disagree. The side and end still meet at 90 degrees.
They don't "know" about the flare if the pins are cut perpendicular to
the angled end, not perpendicular to the piece as a whole. Words fail
me in trying to explain it better.

3. The parts will be right and left. The inside face of the box will
be against the fence. You need to make the first stop and the little
offset block symetrical and moveable from right to left.


Remember that the ends of the tray usually have curved edges that
don't reference well. By using the method I described in my other
post, you can always reference off the edge that will be on the bottom
of the box. That edge is always straight. Use a spacer against the
index pin on your jig to offset the first cut on either the end pieces
or the side pieces. Then all parts are interchangeable and you don't
have to deal with multiple indexes.


Or buy a multi router. They don't show that specific joint but I think
it would do it utilizing the tilting table and box joint template

Never pass up an excuse for a new tool!

DonkeyHody
"We should be careful to get out of an experience only the wisdom
that is in it - and stop there; lest we be like the cat that sits
down
on a hot stove-lid. She will never sit down on a hot stove-lid
again---and that is well; but also she will never sit down on a cold
one anymore." - Mark Twain