Fixture design tips

Hello,

I'm relative new to the trade and struggling with designing a fixture for a part.

This is going to be a small production run so will eventually make a pallet.

The part is about 85x110x19mm made of 20mm thick stock, flat bar.

Today OP1 is facing the backside and contour around the sides down 15mm.
Then I flip it onto a fixture with mitee bite clamps and do the rest of the sides and "inside".

I'm having trouble with the alignment and get a thin line on the vertical sides when contouring in OP2.

Any tips and tricks of how to make this fixture better?

I have thought of buying 25mm stock and doing the inside/outside on OP1 and flipping it onto a fixture for facing and chamfering the bottom. Good idea?

That is always tricky.
I find using a reference bar on the table, against which I push the job, works moderately well.
Failing that, you could consider doing each side separately. The milling time would be very similar, so you would only be up for the time spent flipping.

However, for many jobs I usually start by making a fairly precise fixture: a slot into which the blank sits tightly. After that it is much easier. The time taken to make the jig is quickly recouped.

Cheers
Roger