No drain portal guardian farm

Shulkercraft's no drain guardian farm, the portal design. You kill the three elder guardians, leave the monument flooded, and run soul sand bubble columns that push the guardians through nether portals. They come out in the nether, fall into a soul campfire kill chamber, and the drops run through hoppers into chests while you AFK. No draining, no perimeter, and the build is mostly soul sand and temporary blocks. It gives prismarine shards, prismarine crystals, cod and ink sacs, and doubles as an XP source if you kill in the nether by hand.

Glass the sides in so the guardians cannot get out. waterducks8672's tip is the most upvoted one on the video.
The soul sand bubbles tank your framerate. Set particles to minimal and it goes back to normal.
Expand the storage if you plan to AFK longer than an hour. AwesomeIronGuy has the 28 chests full in about 48 minutes and the hoppers backing up by 52.
If the guardians drop raw cod instead of cooked, swap the soul campfires for lava. The campfires hurt them but do not set them alight.
Build it in the orientation shown. woodrbeofficial rotated it 90 degrees and ended up with shulker boxes full of ink sacs instead of prismarine.
On Bedrock you need a temporary dirt line above the fence gates to get the water to sit right, otherwise it is the same build.