Corner clamps are a great way to hold
I designed (Fusion360) and 3D printed a version that uses replaceable jaws of any shaped. Four screw points are provided on the inside of the clamp body.
The wooden jaws must be 12mm or higher. If needed you can bevel or cut into them when working with thinner stock.
The 3D printed section of the clamp has 2 slots for clamping as well as a third hole. This third hole helps you clamp things squarely on the bed when you use two t nuts on the same t track.
The replaceable section of the square can be cut on your CNC machine or you can use any straight scrap. It can be any shape need as long as there is a 120mm 90 Degree corner for attaching to the clamp body.
Below are copies for the 3D printer STL files and the GCODE for the square jaws as shown above.