A hax0red way I saw using a vice - build a frame using heavy stock lumber, like 4x4's bolted together, you can use a miter box/saw to angle the cornors, for added strength also use metal 'L' brackets on the outside of the frame - basically you want a box with the inside about 6" by 4", though you can knock the size down as needed - the smaller the better .. you can also get a nice piece of like 3" round metal pipe, have a section about 1" tall cut ... in all cases you're just trying to build something for the re-rock to form to... on to the next step - one end you simply need to put a removable back into, such as a plug for the pipe or like a sheet of plywood/metal/plastic to place behind your wood frame, the second part is the hardest part of any press - the 'plunger' of sorts to compress it to the form... you can make it out of wood, make it oversized then sand it to a perfect fit - you want it to be tight, where there isn't going to be room around the sides for coke to escape ..
The setup is for your new press is simple - the flat back suraface, then the frame, fill it with your powdered and cut coke, then the "plunger" .. sandwich it all in the vice and start to crank it... it's going to be difficult and remember leverage - an extended pipe will help, and this wont work with a girls vice, get a big one!
When you're done it should be solid, if you went with the wood frame you can remove everything, set it on a flat surface, and swing down on it with a 40lb sledge - I don't know if you could get away with it using a vice, but when we re-rocked with the metal frame/pipe and 6 ton hydrolic jack, our finished product was very solid..
Lets see... hrmm... hummm... do I want to really get into all this? I know it will only add to peoples coke being cut... well, as I said, IF YOU BUY CUT SHIT ONCE, SHAME ON YOUR SOURCE, IF YOU BUY CUT SHIT TWICE, SHAME ON YOURSELF! .. anyway, for the wood-frame/vice method you're not going to get it as solid as you will with the jack, so just like the towel method, it helps to add a little water - a squirt bottle of a good way... put the coke and cut on a bowl, mix it real good, then take your spray bottle, spray and continue to mix... you don't want to make slop, you just want it to be a little damp when you press it.. here is another Masrtin Luther King Jr Blvd trick - glue.. yup, go get some Elmers School Glue .. put some in the spray bottle and add warm water, mix well - get it as thick as possible so it will still spray ... spray this in your coke and press - it really does help!
Again, I recomend you go the route of a 4-6 ton hydrolic jack, as you dont need any fluid in your finished product - you go from powder to something thats as hard as a pill ...
Alright you shady motherfuckers, go cut your coke, sell your Asprin/Ecstasy, jack off in a bottle and sell it as "Super G" ...