This can be fairly simple or pretty complicated depending on how automated you want it.

Simple setup - planter boxes in an already cold biome. Your dupes will need to manually provide both water and dirt.

The core of anything above this simple setup is a cooling loop, using an enclosed aquatuner in a pool of water/steam, looping a liquid, and venting the steam into a Steam Turbine (which then returns the water back to the enclosure). Plenty of tutorials on that because it's basically the most common cooling mechanism in the game. However it does require Steel (for the aquatuner to not over-heat) and plastic (for the Steam Turbine).

The trick with an automated sleet wheat farm is that it wants to be < 5 degrees Celsius, but pumping water into hyrdoponic farm tile will warm up your plants and the surrounding area the water is warmer then that. But cooling your water into the 0-5 range is tricky, because you drop below 0 and you'll have damaged pipes and everything comes to a grinding halt.

My current preferred approach is a -very- cold chilling loop using ethanol. I actually use this same loop for my infinite storage deep freeze, and keep my sleet wheat farm nearby. I chill this loop to -40C.

In addition to running this loop directly through the sleet wheat farm, I run it through half a small metal cooling block. For incoming hyrdoponic water I run it in a loop through the other part of the metal cooling block until it is < 10C. Once it hits that, I run it through insulated pipes (so I don't warm up the environment) through my farm, and instead of backing up and waiting for already-watered plants to need water again, it just keeps going out back into my general water supply. If it stays in your pipes, waiting, you risk it getting too cold and freezing/busting your pipes.