From my experience, mechanical/hydraulic presses are not practical for the regular DIYer. In addition to being large, heavy, expensive, uneven, and more, they are extremely unsafe. To press longboards I built a large steel press capable of 70 psi (fourty thousand pounds!) but it was very expensive, weighed 500 lbs, and most importantly, the design was verified and assembled by a professional.
Here's the solution for someone who wants to do things like this themselves: Vacuum! There is a huge column of air extending miles above you, weighting down for miles that only doesn't crush you because it's all around you. Remove it from one side, and the whole column comes crashing into the void with a pressure of about 14 psi. That's about 8 THOUSAND pounds for the area I was describing before. A simple vacuum has the potential to safely and effectively replace a metal frame and massive bottle jack, and I've developed a way to do it for about $20.
I designed the part shown below (download here: https://grabcad.com/library/20-vacuum-table-1) to be 3D printed out of...whatever. I use ABS because it's easy to smooth and make airtight. Wipe it down with acetone or clear coat it with some urethane or even just rub Elmer's glue all over it with a brush. Anything you can put on the surface will help keep air in.* The part it difficult to print but once done it is your whole vacuum system. All you need to add is a Vac-U-Vin stopper (get them on amazon for about $8. They're used for sucking the air out of wine bottles) and a zip tie to secure them.
To make the table, use anything that isn't porous. Anything. The best option in my opinion is a sheet of melamine that can be found at any hardware store for a few bucks more than a cheap sheet of plywood. In the lpictures below I just used a shelf! You'll also need vacuum tape and vacuum bagging film, but those can also be easily found on amazon for a very low price.
1. Lay the tape out along the perimeter of what you're going to suck down (add about 5x the height of your thing to the size of the perimeter) and the put the thing in the middle under a few pieces of paper towel. The paper towel should go under the front lip of the part and allows it to "breathe" so that it doesn't just seal by the opening.
2. Take the "pump" and stick it over the tape and add a little bit of tape across the top. Put some paper towels under the thing and under the little edge of the pump. Then just put down the film and press it into the vacuum tape. That's it! You can suck the air out with the little pump and if you sealed the tape firmly enough, it should hold! I usually come back and suck the extra air out every few minutes or so until the glue or epoxy is set.
You can see the results of a few quick tests I did. These all held about this level of vacuum for 10+ minutes! It can be scaled to just about any size, and once you have it together you can slip parts in and out pretty easily. As long as you don't get too much junk on the sealing tape it's possible to use and re-use it dozens if times! It's also possible to make this huge. For larger projects, you can remove the cap of the Vac-u-vin pump and suck most out with a vacuum cleaner or shop vac, and then reattach the top rubber seal and pump the last bit out by hand.
*If you do your own 3D printing, print with about 5 perimeters and bump your extrusion modifier up about 10%. This makes the part look a little messier but really smooshes the layers together and makes it airtight! To get rid of support (if you don't use water soluble stuff) bend a paperclip at an angle and just mash it up, getting as much out as possible. Remember that you don't need to remove all the support material from the inside, you just need to break enough to allow a little bit of airflow.