the real question is what HAVENT you tried? plastic cups, dixie cups, yes handrolled newspaper (im awful clumsy and impatient for those) butter tubs, milk cartons. You name it!
Heres one of my ultimate favs. dishtub from the dollar store. I normally start cuttings in these, but yes some seeds too. These are great cuz you can stack 5+ and drill the drainage holes all at once. zip zip zip DONE!
Im experimenting with another recyclable idea to keep flats evenly moist. Whatever kind you use! Must admit my hatred for watering, especially inside. But the little guys need it... Have you ever seen those burpee raised self watering flats? I was skeptical myself until one was given to me.
This thing is KICKING BUTT. I filled the tray once, the water lasted over a week and the plants are getting exactly the right amount of EVEN water distribution.
BUT theyre $20 bones online. ouch.
Of course, I immediately started doing research. And came up with a homemade version. Still testing, but it looks like it might just cut the mustard.
That's newspaper in there serving as a 'capillary mat' or 'wick' (what CANT you use newspaper for!) Based on this research... https://www.ag.auburn.edu/adm/comm/news/ ... cycled.htm
Also suggested, towels, felt, batting... Im cheering for newspaper because it absorbs any added fertilizer and you can throw it in your garden or the compost bin when youre done.