I want to build one that is strictly vacuum with no glass on top for copy stand use. I was going to use perforated sheet steel for holes. They have a 1/8 or 3/16 inch hole option on the steel. Some companies have smaller holes. I'm thinking 1/8 should do it. I plan to mask off areas with plastic that are not being used to increase suction. I will use a shop vac for suction. Frame to be wood. I may have to use some metal strip in the center to support the steel sheet. Will have to see how much it sags. I was thinking of 24 x 24 inches, but may go 18 x 24 to increase suction. Steel comes in 24 x 24 as standard size. If you want max suction the best would be to build specific size easels. But it is time and $$, although the payment is mostly time as the smaller you go the cheaper it is and $$ is not a big deal. I'd rather buy one instead of making one as long as it was affordable. But all these old school tools are slim pickings trying to find them to buy. Here is one like we used back in the 1970's for graphic arts use. Ours was bigger and more robust. It was on a stand and swiveled for vertical use with process camera or horizontal use. They were called vacuum frames. The glass did not heat in them. They were not hot presses. https://www.bhphotovideo.com/c/product/1190287-REG/drytac_hgp360_hot_press_heated_glass_top.html?ap=y&ap=y&smp=y&smp=y&lsft=BI:514&gclid=CjwKCAjwxuuCBhATEiwAIIIz0dy9-SOcFEBlb25UvFhqGcp3TS1_nnlJiUNJ5Yf8SyCy74G58boykBoCoiUQAvD_BwE They had an old thread at Large Format forum on a home built vacuum easel. Sadly, all the links are dead. Here is some videos on YT. https://www.youtube.com/results?search_query=vacuum+easel I had built a vacuum easel when I was a kid, but it did not work good. The holes were far apart and too big.