There are a lot of ways to make hop water and you can make it as easy or difficult as you'd like. I found a method that works great for me as it's mostly hands off and doesn't require heating the water.
I start by filling a 5 gallon jug with RO water from somewhere like Natural Grocers or Smiths. Natural Grocers is the cheapest in town, especially if you're one of their members (it's free to be a member and only takes an email address). After that, my method is as follows:
Ingredients:
* 5 gallons of RO water
* 1 oz of your favorite hops
* 1/2 tsp gypsum
* 1/4 tsp epsom salt
* 10g citric acid
* 1 tbsp biofine (optional)
Equipment:
* Keg
Method:
1. Add minerals and citric to the keg
2. Add room temp water to the keg
3. Pour hops into strainer
4. put strainer in keg (making sure to tie it off to the outside of the keg so you can take it out easier later)
5. Let the hops sit for 8 hours
6. Remove the hops
7. Add biofine and put lid on keg
8. Attach CO2 set to 25-30 PSI
9. Purge the headspace a few times, then shake the keg like crazy to help the CO2 get into the water
10. Continue shaking the keg a few times per day for three days (I do this at room temp, but it should be fine in the kegerator too)
11. Put keg in kegerator and have the pressure set to 25psi. Let it chill and give it time for any hop particles to drop out of suspension
12. Pour out a pint or two until the water is clear (it may take a few days to go completely clear)
In all, it takes about 10 minutes of hands-on time to make if you don't count the shaking of the keg when CO2 is added.
For hops, I've tried a combo of Azacca and Galaxy, one with just Lemondrop and one with just Mosaic. Of the three, I like mosaic the best. I don't know if it's specifically the hops or I've just dialed in the mineral and citric additions a little more with each subsequent batch.