effectively, one could use twist ties, anything to support the plant stem and root start above the water nutrient. all i use are mini yogurt cups that i sliced in slots. i have had hot lemons 2 feet tall and a cherry tomato plant almost 3 feet until i finally moved it to soil.
only recently did i fill the mini yogurt containers with clean pea gravel, prior to that i just let the plant sit in its starter rockwool, of which being so cheap, i cut my 1" rockwool cube in half, and that i drop into the cup.