Line the baking sheet with aluminum foil. Move an oven rack to the top shelf. Turn the oven and set the heat to to broil.
Cut the peppers in half lengthwise. Slice out the stems. Remove the seeds and white ribs using your hands and/or the knife.
Arrange the pepper halves on the aluminum foil, skin side up.
Put the baking sheet in the oven and broil until the peppers are blackened and collapsing, about 15 minutes.
Using pot holders, carefully remove the baking sheet from the oven and set it on top of the stove. Still using pot holders, gather up the edges of the foil so that the peppers are mostly inside a kind of foil tent, and leave them to steam and cool for 10 minutes.
Peel and rub off as much of the blackened skins as you can. This is messy! Just do your best. If you’re using the peppers right away, they’re ready now. If you’re preserving them for later use or gift-giving, move on to step 7.
Put the oil, vinegar, garlic, and salt in the bowl and add the pepper halves. Use your clean hands to make sure that all the peppers get coated with the oil and vinegar mixture.
Divide the mixture evenly among the jars. Screw the lids on. Refrigerate the peppers for up to one month.