Jessica Hische (of the aforementioned occasion) was kind enough to share with Apartment Therapy the process she uses to create her prints:
"When doing the printing myself, I send my files to Boxcar Press. They make polymer plates from my designs - one for each color. Plates are like large stamps that the design is developed onto. With letterpress, like most traditional printmaking mediums, you must print each color separately. The Viney Alphabet Poster is a three-color print so it required three plates, which came out to around $400. Plates can get expensive depending on how large they are and how many colors you're printing.
Once the plates come in, I reserve time at a letterpress studio in Williamsburg, Brooklyn called The Arm. If you know your way around the presses, Dan (the owner) charges a low hourly fee to use them, and is on-hand if you have questions. He also offers group and private lessons for people who want to learn. I cannot praise this place enough. It's awesome.
I have my paper (Crane's Lettra) cut before I print so everything is perfectly sized. This won't be the final trim though, as you'll need to remove registration and crop marks after you're done printing, so the paper should be at least an inch past your trim marks. It's important that all of your paper is uniformly trimmed so you can register, or line everything up, correctly.
These posters were printed on a Vandercook #4, which is a big hand-cranked press. The ink is spread onto plates with rollers, and then paper is pressed onto them to actually print the design. Each color is printed separately, so since this was an edition of 250, I had to run the paper through 250 times for each plate. If you do it all in one session, 750 cranks can result in a pretty swollen hand! Each time you switch colors, you have to secure a new plate in the press, and it has to be re-registered. I recommend bringing throwaway paper cut to the size of your print for this process, so you don't waste a ton of expensive letterpress paper doing these alignments.
After all your printing is done, all that's left is the final trim. You can have this done professionally, or do it yourself as you sell them. Finally, signing and editioning. Done!"