I agree with goober. Also keep in mind those who are considering using the dremel method that these carbon steel frames will not cut as soft,smooth,or fast as aluminum. Ar lowers are one thing but these are not the same ease to cut. It's still very easy and simple and very doable with at least a drillpress and vise. Just take extremely slow and light cuts for the rails and the barrel seat with more caution. With a mill I'd say this is a 30 min project without fitting the slide.
Looking at the 3d rendering for the jig,the depth for the rails are set so as long as you can move the jig straight on an even table it's idiot proof and you would hit the jig before going to deep. The barrel seat is the same concept however milling on a still press does create some wobble that could wreck the lower if you apply too much pressure as it would go out of spec. And the two holes are common sense to use a drill press.
Brownells sells a lapping kit I think to fit the slide on a frame with lapping compound and alot of time. Since it's one of those tools we only use once in a blue moon I'm sure we can all share them from area to area