It is often that we overcomplicate things, this should be the motto of engineers everywhere.
How does this relate to today's topic? Well, here we go!
4 couplers and 4 bolts
perfectly acceptable and adjustable bed.
Up to this point you are around 12 bucks in and if you add a few magnets to make this easy detachable you reach new heights at $16. You could stop here and just use the existing the aluminum piece that came with the laser.
True, you would have to patch the giant hole in the middle with some aluminum tape, but I would not judge.
If you are against that idea, you will add a few more bucks to get a piece of expanded steel. This is the point were you can stay under $20 or quickly make your way to $50 or more if you go after the glamorous stainless steel. Even if you go for the regular perforated steel but you like it a little thick you will find a bill/bit less in the wallet after.
Now that we got the mercantile aspects out of the way let’s talk:
The coupler is 1.75 inches long, that is around 45 mm for the rest of the world and 3/8 or about 9.5 mm in diameter. It is generally used for coupling thread rods hence the coupling nut name. The bolt is also the same length and( should I really need to say this?) diameter. If we take in account the .25 or 6mm that you lose in the engagement of the nut with the bolt we are left with 1.5 inches /39 mm or so of adjustment. This should be more than enough for most humans. If you need more adjustment, then you may need to invest more than $20.
You can bolt the couplers to the bottom of the case for extra stability of you can use magnets like I did. A few neodymium magnets will keep everything nice and tight but will allow you to remove everything in seconds. That is something to consider if you have rotary attachment. Bolting would also require bolts and preferably short ones. I was able to find .25 long 3/8 bolts locally but I had to hunt them down. The bolts will also take away from the maximum adjustability as they will occupy the bottom part of the coupler.
Adjusting the bed
You will need to make a focus gauge for easy adjustment.
The general practice is to cut a ramp and determine the focus. Measure the distance between the head and the ramp at that point and use this to make a focus gauge. Once you have one you can use it to adjust the 4 corners using a hex/Allen wrench. You will need to do this independently so obviously this will take an extra 30 seconds. If that is too long, you need to train and be faster. Think Rocky and Eye of the tiger. Now you will hum it throughout the day. Teaches you to complain!
In conclusion, these nuts and couplers can be found locally so there is no reason not to grab them and get to work.