It is a second time already that I am growing cacti from seeds. I came up with an interesting way of doing it.
I had an old 5 gallons fish tank, and I decided to germinate seeds there. I put the clear food wrapper on top and made sure it's airtight. I also put the small heating pad under the tank.
I had a growing lamp on the top and I didn't uncover the food wrap for 10 weeks.
Here are the results of my successful experiment: