First task is to decide out how the boards will fit, taking grain direction, and reference side into consideration and to mark out the panel. The task is easier for these panel because they will be painted so no need to include figure in the decision.
Here is the first panel marked out with a furniture maker's triangle, face mark, lines across the joint line to help aline the panels while prepping the glue surfaces, a ">" to show expected grain direction, and a "A" to indicate panel position in the box:
After marking out the panel I put pairs of the boards in the vise to true their glue edges. The first step is to create a shallow hollow in the middle of the glue edges:
Then come back and take full length shavings:
Glue pot warming up the liquid hide glue:
Glued and cooking:
Just three more to go before starting the dovetails.