Place an oven rack at the uppermost spot in your oven. Preheat the broiler.
Lightly spray avocado oil on a baking sheet lined with aluminum foil. Place chiles on the foil in a row; lightly spray them and place under the broiler.
Check the chiles every couple of minutes. Pull out the baking sheet, flip the chile peppers over to get an even char. This will take approximately 5 to 8 minutes from beginning to end; check the chiles every minute as they get closer to being done.
Once the chiles are charred on both sides, use the tongs to place them in resealable plastic bag for 15 to 30 minutes.
Wearing gloves, remove the charred skin on the chiles. With your hands, split the softened chiles, scrape the seeds from the inside, and discard the stem.
Let the chiles cool on the counter before placing them in an airtight container for refrigeration. See notes for freezing instructions.
Notes
Once the chiles have cooled, refrigerate in an airtight container for up to 3 to 5 days, or freeze the chiles in a single layer in resealable freezer-safe plastic bags, squeezing the air out, for up to one year. You can chop the chilies if you prefer and place them in quart size freezer bags for smaller portions.
Once the peppers are peeled and chopped, figure approximately 1 ounce per serving. which is approximately 2 tablespoons. This can vary depending on the heat of each individual chile and each person's tolerance for heat!
Instead of broiling, roast them on a lower oven rack in the oven at 425°F for approximately 20 minutes until they start charring on the outside.