Here are a few pics of the vacuum table I made. Bottom is MDF top can be MDF or ply, Table insert is MDF and can be turned over and end for end as need for a fresh surface. Finger hole to allow for easy removal of the insert.
Picture of table inserted. Note the battle damage, I engrave 0,0 lines before I start using it.
The insert is 300 x 200 there is a margin around the box to allow clearance for the laser shroud.
The entire table is held in with 2 clamps on the left and front, There it butts up against 2 stops/slats super glued to the base plate for registering the table when removed replaced.
Total height is 30mm to allow it to be slid out the right side.
Vacuum is a Festool, very quiet, I previously built one to use on my CNC using a Bunnings wet and dry vac.
This photo is of it with the inset removed. Note the wood inserts overlap the hole and also the 2 near the center
act as a divider making 2 chambers - they help even out the vacuum and also prevent the insert from being sucked down when the vacuum is on.
The margin under the cover is ducted around to the center - this is a previous one that warped while I was building it so I had to start again.
Ply placed on top, finger holding one corner to show total warp
I usually place a paper towel on top of the insert then the work on top of that, any extra holes I place a piece of paper over.
There is a gate by the vacuum inlet to allow reduced pressure.
Fumes are also sucked out once the cut is started.
I have a CNC and can do any number of holes on the insert, The first test was done using peg board, worked fine
It took about 4 hours to make but has saved a lot of time as I don't have to tape things down.
If the material you are working with is severly warped, while it may flatten under the vacuum, cutting may allow it to spring up again.