The pics are of 1. a bridge sunk into the body; 2. the head of the guitar showing the angle ali, nut mentioned later, (it could have simply gone from side to side and painted over - I was being "clever" by routing it inside the edges
Making your own is a good way to go. The neck thro' body can be a plank of anything solid and at least 1.5inch thick. You can start with a straight plank for neck through to bridge and add "wings" for the body; That's what I've done here. With a bandsaw I could make curves, but it doesn't have to be guitar shaped and straight lines in the body will do, like the "New York skyscraper" styles.
The bridge and nut can be made out of angle metal (ali, brass, steel ....) using a hacksaw and files. You used to be able to get ali offcuts from those guys that make window frames. I got loads of stuff from one; angle as above, narrow channel for PSG knee levers, wider channel for knee lever mountings and also for lap steel bridges*. All free as they were too short for him to be bothered and not heavy enough to weigh in.
The bridge needs suitable "nicks" (for the string ball-ends) in the edge of the part that sits on the guitar top and you might need also to rout a grove in the body for them (like in the gold-top pic).
If using *ali channel, you can drill holes for the strings in the back edge (cut it down from the height of the front "bridge" part). That type can be screwed straight down without routing the guitar if you like.
One other tip if you use angle stuff for the nut, screw it down with the return under the fretboard rather than towards the tuners. Saves space and looks neater although you need to rout out the housing for it.
The other pics show another homemade (it doesn't matter that they're 7 stringers) and you can see the head is a simple router job after planing it back to a slight angle at the front. The other shows the bridge/tail, this time right at the end. Both pickup and bridge covers are bits of thrown-away Fender bass covers (who uses them




