Best and cheapest method I used was with actual 5 gallon/20 litre buckets/pails elevated with a hose/tubing coming out the bottom, bent up the side of the bucket and held in place with the bucket handle.
The outlet can be low down on the side instead but I prefer to totally empty the bucket. Some people use inline pumps or only top the water levels up and don't fully change the water out. Some pre-made units have a water level indicator tube that can be swiveled around to drain the bucket.
I have scrogged a 4x4 using 1 bucket, 2 buckets, and 4 buckets. 4 buckets was faster to fill the net but more work as I changed water once a week. 1 bucket took longer to fill the net and would have to be topped up almost every day it drank like an alcoholic, the PH would swing wildly from morning to night, rootmass was huge. 2 buckets was somewhere in between. Occasionally I had to be away for days at a time, so the (laziest) solution was a one plant scrog in a large 160 litre tote. I could be gone for a week and not have to worry about water levels, the PH would swing less drastically, and I would exchange the water only every 2-3 weeks, sometime only once after flip at 4 weeks with PH/EC and water level adjustments in between. Tuning the PH can be a bit of a bitch tho if you have large root masses and are not fully exchanging water.
