WHAT YOU NEED: Can of tuna(empty preferred, see below), clamps(c-clamps suggested, use what ya got), 'baccy, stove
Open a can of tuna and empty it. Retain the lid.
Turn the tuna into tuna salad, make a samich. Enjoy.
Whilst eating the samich, clean the hell out of the can and lid. Soap and water work well, but if you want to be extra-sure, run it through the dishwasher or hit it with a light bleach solution.
Line the can with parchment paper; cut a circle each for top and bottom and a strip wide enough to wrap around the interior diameter of the can.
Bottom circle in, inner strip in, then pack the can with the 'baccy of your choice. Put the top circle on, add the lid, then clamp *sorta* tight. You want to compress it, but you don't want to turn it into a 'baccy puck.
Fire up the oven to "warm" or whatever your lowest setting is. Pop "tobacco press" into oven on a piece of foil or baking pan(get your significant other's permission or things could get ugly). You might want to play around with the temps if you do this more than once, but "warm" seems to do alright on my stove. YMMV.
Allow to stove for as long as you think necessary. I've done 8 and 12 hours with MacBaren #1 and it turned out alright. You can control humidity a tad by leaving the door to the oven open for a stretch here and there OR by directly spraying water onto the contraption and closing the door. Just keep an eye on it and you'll be alright.
DISCLAIMER: I've only ever done this 2 times, so I'm no expert. But my kitchen isn't burned down and I smoked all the tobacco I stoved and haven't turned into a newt yet, so it's pretty safe.