I spread paper towels on a bunch of cookie sheets then spread thin layers of gravel and let it air dry.
Then put in a clean container with a lid.
Short term - in 5 gallon buckets with dechlorinated water.
Long term - not had this situation yet but... I would probably dry it and store in 5 gallon buckets.
If it's going to be used soonish, in a bucket with an airstone.
Otherwise in bins under the fish unit.
I have stored wet as well as dry, I prefer wet with a sponge filter in it.
Mine gets spread on a trash can liner in the driveway. to dry in the sun for a few days.
After that a covered five gallon bucket or tub.
ive always put it in 5 gallon buckets, and left it in the garage with lid off for a few weeks for it to dry off.
then snap a lid on, and stuff it out in the shed.
just be sure it is dry before sealing it.
I usually rinse it in tap water thoroughly.
find a rare sunny day and air dry it or most times I use a hair drier that I bought specifically for this and dry it by hand.
Then toss it in a bucket and your good.
It's only about 30-40 lbs, so I'll probably get a 2 gallon bucket and store it in that with a sealed top after it dries out.