so this is a very simple setup for making crystals

1 = stockpile gate that checks the if LESS then X
2 = Counter gate on how many ants can enter
3 = checks IF carrying crystal
4 = stockpile gate checks if MORE then X
5 = old gate

so both stockpile gates check the stock pile of the crystal itself
when the ants enter they pick up the crystaline at the dispenser
then they go into a loop until it turns into a crystal to put in
into the stockpile.
then it continues or leaves depending on the amount a stock you set.
do keep in mind this takes a fair amount of energy.

i let 3 ants in atm you maybe can do 4 or 5. but make sure you have the energy for it
putting a pin in the middle doesnt really make a big difference but can help out a bit.

Tip :
thanks to Jan
Placing a light beacon in the middle or close to it speeds up the production.