I get asked about these often, they really are very easy so just a few pictures, as my spoon blades are are forged with a round tang as well this method is directly applicable.
Roughen the tang section that you want sunk into the handle with coarse paper. All the blades are left with the final polishing compound on as this protects against rust but a wipe down with some solvent will help to keep thing clean during the handling process.
Drill a hole that the tang will fit into. I get it as straight as possible but if it is slightly out of line would advise rotating the blade until you get an orientation that suits you , I have heard from some people that a leading edge is desirable, others have said trailing.
I always seal the handle with oil first that way any excess glue won’t stain the handle. Then mix up some epoxy and dribble it into the tang. let it settle to the bottom of the hole for a few minutes.
If you judge it perfectly when you push the handle in you will get a nice fillet of epoxy showing. Remember it does soak into the wood and shrink slightly on drying so if you wipe it off flush you will probably end up with a crater when it is set. if you have put to much in wipe it off with a tissue as it goes in.
Check you you are happy with the orientation, the put aside to set. Another coat of oil and you are done.
I am off about to leave for Barn’s Green Wood Guild to teach a course, hopefully there will be time to put together a quick video on how I sharpen and explain the edge geometry on these curved blades.