you heat the water to 80C, dissolve your product in it (ratio 1ml to 1g), then pour the solution into a thermos. tightly close the thermos and leave alone for 2-3 days. after a while, you open the thermos, drain the water from it, remove the crystals from the bottom of the thermos (these are the lumps like in your photo)
Apparently two days was not enough. the solution has not had time to cool sufficiently. but this is a very good sign. Your thermos is great. try leaving it for 5 days. I am 100% sure that the result will please you very much. I'm serious. just try it and you won't regret the crystal will be huge!!!
it's like that. you got a supersaturated supercooled solution. but the centers of crystallization were not born (there was not enough time). you opened the thermos, disturbed the solution and an avalanche-like crystallization occurred. everything is exactly as it should be in such cases. it means you did everything right. just need to give more time