I keep seeing this thread and mulling it over.
You want plenty of skin to wrap over the end, so slice around the last section of useable skin, peel back the good skin towards the hand by 3/4 of an inch or an inch – I guess you probably need to cut down lengthways as well to make it easier. Going back a step, a tourniquet (zip tie) is probably a good idea. And turn your soldering iron on, clean your tools, clear your garage worktop a bit, go for a wee etc.
After you’ve got your skin flapped back, cut 1/2 inch back from where you cut the skin. slice through all the soft bits, cauterise bleedy bits with the soldering iron then get your dremel or hacksaw out ( I think I’d go for the hacksaw, personally* – medium tooth for wood, plastic etc – treat yourself to a new blade, why not, and clean it beforehand) and get through the bone. Rinse, spritz of IPA (not the beer). Flap the skin back, make good. I’ve got some sharp new flush cut snips I’d use to cut the skin so it joins neatly. Probably use more of the palm side, less of the back. I’d probably glue rather than stitch, as I’d be doing it one-handed, and I’d probably have had enough of the whole thing by then anyway. Hopefully the finger in question is on my left hand, because I think my right hand is a better surgeon.
Have a drink and a sit down, mop up, then drop into minor injuries to check my work.
*Maybe a bandsaw if I had one. Harder to clean beforehand, though… And after.