It's just electrolysing water into hydrogen and then using the hydrogen in a Haber-Bosch reactor with nitrogen from the air to make ammonia. Electrolysis is easy enough to do on a small scale.

Fritz Haber initially demonstrated his process producing 125 milliliters per hour of ammonia in a "tabletop machine", so it's obviously technically possible. Typical process parameters are about 200 bars and 500 degrees C, so it's not trivial but also not outside of what a dedicated hobbyist could reach. I'm pretty sure it's not economically feasible at small scales though. Even the earliest industrial plants in the 1920s made 20 tons of ammonia per day. It will be vastly cheaper to just buy the stuff in bulk from a plant churning out hundreds of tons per day than it will be to make it yourself at a rate of 2 liters per day.

That said, go for it! A factory is just a room, and similarly a chemical reactor is basically just a steel drum.