Cold brew. Take an empty juice bottle, 64oz., say, and fill it 2/3 with grounds. Doesn’t need to be super extreme premium quality, cold brew is very forgiving. Fill to the top the rest with the best water you have. Shake it a little. Put it in the fridge overnight; minimum 12h, maximum 36h.
Then set up a filter; a chemex works great for this. You’ll go through about 6-8 filters with it. Put in the first filter, shake up the bottle really good, and pour into the filter. You can keep topping it off until the grounds fill up the filter.
Either let the brew filter out (about 20m or so) or wait awhile and carefully squeeze the filter (not recommended; if you can wait, wait.). PRO TIP, when done, put the filter in it’s own plastic bag before throwing it away, they will leak. Produce bag or amazon mailer bag works well.
Once you’re done, you’ll have a strong cold brew concentrate that will last a week or more depending on how much you make. An old clean ketchup bottle, like with the squeeze-top on it works well to store it in the fridge. Enjoy!