While I have a shooting board with a 90° fence, any other angle requires fussing with wood, screws and a protractor. In a moment of desperation, I cut a groove down the center of an old bench hook that matched the standard miter groove on my table saw and dropped in my miter gauge.
I had to unscrew the T-slot guide from the end of the gauge, but this provided a perfect, non-destructive way of anchoring it in the slot using a counter-sunk screw into the bench hook.
I calibrated the fence against the edge of the bench hook in the same way you would if using the miter gauge in the table saw: Loosen the calibration screws on the gauge, grab a square, nudge the fence until it’s 90°, then lock the calibration screws.
The shooting board now has a fence with a built-in protractor, and positive stops for more angles than a politician running for office. –Barak Bruerd