Filé powder?

When I dug my sassafras roots for tea a couple of days ago, I uprooted a few young sassafras suckers.  Some of the leaves in the top part were quite tender, so I thought about trying to make some filé powder, which I'm told is used in some gumbos.
I washed the leaves, put them on a paper towel, and microwaved them for about a minute, I guess, in 30 second intervals.  (I don't remember exactly.) 

 

After I took my blackberry pie from the oven,

I let the oven cool some, and then I laid the paper towel and leaves in the oven and just left them overnight.
The leaves are nice and dry.  I put them in a plastic zip bag.  I will probably just rub them in my hands to crush them.  If I had a larger quantity, I would probably use the blender to grind them.
Now, I just need to find a suitable gumbo recipe.