On this engine I went for a silver soldered bronze/brass fabrication for the cylinder though it could also be done fairly easily from a solid piece of cast iron or even bonded together with JBWeld if you did not feel upto soldering.
The cylinder consists of a "cylinder" cut from hollow bronze bar bored under size and with a spigot each end.
Two discs of brass fit onto these spigots, these can be cut from round bar or as I had quite a bit of brass flat I used that. Again made slightly over thickness.
The last part is a block of bronze flycut to overall size but left a bit thick, curves added with a boring head and the passages milled in.
After waving the magic torch at the parts you have a basic cylinder "casting" that can then be bored to finish size, have the flanges machined to thickness and the port face cut followed by milling the ports and drilling & tapping some holes.
The two other parts that need fabricating are the bed plate which as Peter ha smentioned is screwed and JBWelded together from 4 bits of aluminium as it's easy to machine.
And the column which is a bit of 10mm flat bar with 3 thinner bits of flat stock silver soldered on though these could probably be done with CSK screws and JBWeld. Once soldered all the critical faces can be machined at one setting which makes sure the top and bottom are at 90deg to the cross head guide.
This is the basic "naked" engine.