1. Buy them whole. Don't buy them pre-ground because after grinding they quickly go rancid, vs as whole seeds they don't go rancid.
2. You do not need to grind them anyway. Just put a spoonful or two into a glass of water and go away for awhile (I forget if it is 10 minutes or more like an hour). Later stir the glass and you will see that the seeds have made a thick gel in the water. Stir and drink it, seeds, gel, water and all.