Iningolob, to hook a sand flea, insert the hook through flapper on the underside, into the body of the sand flea until the point of the hook just pierces the main shell.
Thanks for the tip CA...Sounds like next time one of my friends comes up from Florida in the fall, he is going to rake some live fleas before he leaves.
Gottog, they will freeze, but become a little delicate. If you hook them the way I described above, they will stay on the hook reasonably well, even when frozen and thawed.
Gamakatsu