Any time you make a frame-and-panel assembly, and especially with hand tools joinery, some of your joints will be a bit out of line. It’s nothing to be embarrassed about – it happens to all of us. The trick is to be able to make corrections for the irregularities with a minimum of effort. The best time to do this is before your final glue-up, and this is the technique I use:
Dry assemble the frame, and look for any places where the joint is out of line. When you find one, use a pencil to mark along the edge of the adjoining piece.
This will give you a guide line to show you the material that needs to be removed. Take a hand plane and plane down to the bottom of the pencil line, feathering the cut in from what is the left-hand edge in the above photo for a smooth transition. As you get close, stop and make at least one test fit to double check – it’s easy to overshoot. Once you’ve planed to the bottom of the line, the joint should be a near-perfect fit.
Give it a try!