Drop in slot? You mean the channel the bar lives in? Take out the allen screws, place the caps and riser bodies around the bar, install the allen screws, loosely. Harley risers come in 2 thread sizes, 1/2-13 and 1/2-20.  Place the risers over the top triple tree holes and install the base bolts. FYI, those are NOT rubber mount risers, they are hard mount risers... Crank the snot out of the allen bolts once you doublecheck that the bars are properly centerd and where you want them angle to the fork-wise. All there is to it.
-WD

Riser bolts are about $3 at the hardware store. By the photos, you need a 1/2-20 by probably 2 inches long. Grade 5 are best for said application, although, standard grade bolts will suffice in a pinch. Pop the rubber mounts off your stock risers and use them to fill in the space in the top tree. Won't hurt the risers or the tree any. But you'll likely need to hog out the bolt holes in the rubber mounts a bit. Haven't popped off the Savage risers yet, not sure what size the mount center holes are.
-WD