I built this spin tester this year.I put a good, straight field point in the arrow and make a reference mark on the tape in front of the point.I turn the arrow so the blade is horizantal and align with the dot.I then turn it 90 degrees so that the blade is vertical,and check alignment there.If it lines up with the dot,both ways,it's perfect.
I used to spin mine but in checking them on this tester,I wasn't as good as I thought.
You don't have to make one this fancy.It could be 2 "V" blocks made of wood or metal angle with notches in it etc..then a block in front of the point for a reference mark.My roller distance is 8" apart.I don't know how critical that is but you don't want the shaft to bow when you turn it.
My last ones,I used a paste epoxy called Ultra Smooth.It gets fairly hard in 3 hours and full cure in 24.I glued up 6 broadheads,let them sit for 1 1/2 hours,at which time the glue was firm but still moveable.I then aligned them and set them aside.