Just let them dry out I would say 90% and then put in a ziploc bag in a dark place and open ever so often and pour out on a baking sheet evenly or something like that to put on, once every couple weeks to check and make sure no mold and to just let it air out. Hash leaves will last a long long time doing this. Also I dont think freezing is good at all it creates all types of moisture and could lead to huge mold problems my opinion.