Well........I've done a fair amount in various ways. I know I can epoxy, solder, drill through and pin, etc. etc. What I'm trying to do now is replicate the traditional method. When I was a kid I tore apart a boy scout pocket knife to learn how it was made. There was this internal stub on the inside of the bolster that went through a hole in the liner. At the time I never thought about how that stub came to exist on the inside of the bolster.
On another forum dedicated to knives I asked the expert and he said they were "chopped". I asked what "chopped" meant and he never gave me an answer.
Possible Answers:
1. A cold chisel "chopped" away surrounding metal- leaving a stub. An apprentice in a cutlery shop could likely do this for a nominal expensive.
2. A pin was staked into a blind hole.
From what I have learned so far the earliest pocket knives had iron sides (bolster and liner) that was forged from a solid piece. I believe a drop hammer and mandrel were used- an iron bar heated red and held over a form (mandrel) and the drop hammer forged out the thin flat liner part and left the bolster area thick. A hardy cut to length. Holes were punched and maybe reamed/drilled true.
In the early 1800's and then coming on strong mid-1800's was the appearance of less expensive sheet metal and metal stamping methods. Now a thin liner could be stamped and the bolster "applied" to the liner. As stated the bolster could be chiseled so as to form the stub that went through a hole in the liner. The blind hole and staked pin could have also been done. I have tried to find out how things were done but haven't found an answer.
Off hand, being a person of modern times, my feeling is the cheaper method would be to drill the blind hole and stake the stub in place. The trouble is, some of the early bolsters are very thin, you don't have much wiggle room in drilling the depth of the hole- it has to be deep enough to stake a pin but too deep and you'll go all the way through the bolster.
On prior attempts I soldered bolsters to liners. If the liner is very thin when the joint cools, on occasion (not always) you can actually get warped liners. I am told the early knives never used solder to attach bolsters to liners. That boy scout knife- when I punched out the stub the bolster fell off, the stub was the only thing holding it in place.
Finally, the traditional method IS THE THING. For example a rat tail knife tang through a one piece wood handle. I could use traditional cutler rosin or epoxy glue- no one will ever know the difference. BUT I KNOW, so I use cutler rosin (boiled pine pitch and powdered charcoal or brick).