Put the handle on the edge of the bench. Then assemble the latch and spring and hold it together with a 1/16 pin punch inserted from below.
Drive the pin in from the top and the other punch falls out.
Make sure it is below flush or you will damage receiver.
No need to let the wife know you have an AR!
Brownell's carries the pin, bit you might be better off cutting some drill rod to length if you are using an extended latch.
The stoopid CF latch broke so often they were replaced with solid pins.