I hope this doesn’t confuse you:
Lens boards manufactured by the camera maker are typically machined (if made of metal) to a tolerance of +/- .0005 inches (.01mm) all around, with what is known as a surface finish of about 4. That translates to a fairly fine finish (equivalent to a piece of wood sanded with 120 grit sand paper), but with enough grab to keep the lens from twisting, or vibrating off. The boards are usually made of the same material that they will be mounted to, i.e. aluminum to aluminum and usually with channels or runners to block light. Thos channels and runner are also made in a certain length or thickness to keep the top of the board to the top of the mounting surface.
If the material of the board is wood, then tightening the lens onto the board will compress the wood and keep the lens from rotating due to surface friction.
Moist wood will swell keeping the lens on, but once the wood dries; the lens can come loose from the wood shrinking.
If you shoot macro with the camera, the flatness and tolerance of the board becomes critical. You want the lens centered on the board with whatever board you use, home made or not. ( I learned that one the hard way).
Not all LF cameras have full movement. If you want full movement, then look for that when shopping around. Also look to see if the lens has a ‘T’ setting. Not all do.
The ‘T’ is for time, and is used to keep the lens open while you set up the image.
Don’t forget a GOOD loupe. The loupe will determine if your image is truly in focus or not. One of the real advantages to LF is the greatly enhanced sharpness of the image. You are now dealing with a virtual 1:1 ratio on the image capture area, and can capture detail nearly impossible with either a 35 or MF.
If you buy a monorail, check to see if the friction wheels are working properly or not. Those friction wheels will keep the bellows from moving around too much, and can be a major headache if they are not working properly.
What ever you do, GET A SOLID HEAVY TRIPOD!!!!! You will thank me later on that. Do not get a cheapy at the local photosplat place. A solid tripod will keep the camera from vibrating, and keep the image sharp. If you can, go with Nikor, Sinar, Schnieder or Fuji as mentioned above. They are pricy, but worth it. For a 4x5, go with as large a piece of glass you can get. The more coverage area, the better.