There's a bunch of things to think about when using captured slides or keys.
I use a very small finishing nail, cut to about 1/4" long with side cutters, and predrill a hole just a hair smaller than the nail straight down the vertical face of the barrel channel wall, in line with the slot in the key. With the key installed, the drill bit can be felt dropping through the slot into the wood below, but be very careful here. Once the drill bit drops through the slot, I only drill down about 1/16" further, because you must remember, the stock forearm is convex now, and the drill bit will come right through the side if you go too deep. All that is required is for the nail to enter the wood under the key a tiny bit, to prevent the slide from being pulled all the way out of the forearm, and subsequently, lost. Likewise, you cannot yard on the slide when you pull it out, or you might tear the slide right out of the wood.
It is rare to have to remove the slide once it is installed, but if you think you might want to do so in the future, use a small gouge to cut away the wood in a circle, especially on the fore and aft of the pin, so that the head of the nail is exposed. Then, a pair of needle-nosed pliers can be used to withdraw the pin.
Sometimes the slot in the key needs to be lengthened so that the key can be withdrawn far enough to clear the loop in the barrel. I ground the set off both sides of a hacksaw blade for doing this job. Then I clean up the slot with abrasive cloth pulled tight through the slot. Sometimes too, the slot is too narrow for even the smallest finishing nail. Then simply file the nail thinner, and set it into the hole to align with the slot in the slide.
Personally, I really like slides rather than pins, when they are appropriate. I remove my barrel for cleaning, every time, and the slides make this easier than pushing out pins. My Kuntz and Verner rifles, and of course, my Hawken all use the captured key/slide. I'll see if I have some pics of those installations.
This is the forearm of my Verner rifle at the third slide (of four). I made the slides by cutting steel stock down the middle with a hack saw, and then silver solder on the head.