If yours doesn’t, bore one out by gently twisting a wooden skewer about 3/4 down (but don’t push it all the way through.
If you need to buy the humidity dome and also need a heat mat, check out the Soligt tray with humidity dome and heat mat ($27).
What is rockwool (definition)?
Here are the basic steps for germinating seeds in rockwool:
IMPORTANT NOTE: Use pH Down sparingly as it’s a strong acid and will quickly bring down the pH level if you use too much. I ended up going too low and had to add more water to bring the pH back up. Better to be more conservative with this stuff.
The pH Meter I bought was new so even before I could start soaking my cubes I needed to calibrate it first.
Remove Cubes and Let Drain
Sure, you can grow autoflowering plants using rock wool cubes outside or inside. If you are using the large cubes you can put them into a fabric container, plastic, etc., but they do need a place for the water to run out of them when it rains and when you water.
Don’t get too deep. No more than a quarter of an inch.
Soak the Rockwool Cubes
Another tip I learned is to not squeeze out or shake out the water from the cubes. You want the cube to be damp as the wetness is what helps trigger the germination process.