I built my wood shop workbench about 25 years ago and the hardest thing about it was not having a bench to build the bench. Sometimes holding your work is one of the things which takes up as much effort as the work.
I started carving a gargoyle a while back (do you have one? Don’t judge me) and holding that thing was a real chore.
One thing I added to my bench recently is a holdfast. The traditional forged ones simply drive into a hole in the top of your bench a little bit like whack-a -mole with your bench mallet. They have a flat hook on the end and the sideways pressure in the hole locks it in place. You loosen it by whacking the shaft sideways. Works like a champ and sometimes you can find a local blacksmith to make one for you.
A more modern version has a small screw on top of the clamp part, and fits into a metal bracket set in the top of the bench. It is related to the traditional style in that it locks into place with a sideways warp in the bracket. To use this clamp, just drop it in the hole in the center of the bracket and then a quick twist to the screw puts a large amount of pressure on the work. To release the clamp, loosen the screw and then pull up on the top of the shaft. The grooves on the shaft release from the grooves in the bracket and it is free.
Installation is simple once you decide where it needs to go to be most useful. You can use a simple straight hole in the bench and it will work fine, but the better installation is with the bracket. I drilled a pilot hole in the top of my bench, and then used a larger hole saw to drill in the depth of the bracket flange, plus a little bit. Then without removing any wood, I used a smaller hole saw to drill all the way through the top of the bench still using the same pilot hole. That way I had concentric holes and could chisel out the flange depth by hand. Worked like a champ after I dropped the bracket in place and added some screws.
Between the new holdfast, my new leg vise, the shoulder vise on the end of the bench, the bench dogs on the top of the bench, the bench “L” vice on the end with two clamping points, and various and sundry other pipe clamps, I bet I could clamp a herd of cats.