If you use a lot of filé powder then this tutorial will be right up your alley.
One thing you will be sure of if you make your own is the quality of the product.
If you don't use a lot then maybe it's because you don't cook much, don't do a lot of Louisiana Creole or Cajun style cooking, use a different 'thickening' agent such as roux or okra or because you don't want to spend the money on a spice / condiment that will be used once or twice and then just sit around.
If you live where Sassafras trees ( Sassafras albidum ) grow ( generally eastern U.S. ) then you have a great opportunity to make some filé powder and get to know it's benefits. A great 'thickener' and taste additive to stews and soups after cooked, and it's free for the taking.
You can make filé powder with just a few kitchen items and some dried Sassafras leaves. A food processor or blender is not required, although helpful.
Mesh laundry bag.
To get started into this filé powder making process it's best to do it in a little way for the first time.
Collect about 50 leaves.
Snip off the leaves that are in the most pristine condition and put them in a bag. I like to gather sassafras leaves in the middle of summer, around August 15 or so, to get them at their absolute best.
A thumbnail will work to snip / break the leaf off. If you don't have a thumbnail cut with knife or scissors.
When home put all the leaves you collected in a bowl of water and let soak a few minutes to loosen anything on their surface that may have accumulated during their growth. After about 10 minutes of soaking wash and rinse a few times.
Wash well, that is, rub the leaves between your hands to make sure any tough adherents come off.
While doing so remove any that do not warrant keeping.
After the leaves have been thoroughly rinsed put them all in a mesh laundry bag and hang outside in a well ventilated area and under some shade.
Every 15 or 20 minutes or so shake them up to make sure all the leaves get air.