Thinly slice them using a sharp knife and set them aside.
Combine vinegar and salt in a non-reactive bowl. Add the chilies and garlic and cover the bowl with cling wrap. Set this aside for a few hours.
Drain the vinegar and pack the chilies with the garlic in a glass jar. Pour in the olive oil until all the chilies are covered.
Notes
Remove the stems and discard the seeds from the chilies if you prefer a more subtle, toned-down version. I do the same when I make my green chili pickle and pickled turmeric.
Don't discard the oil- it is actually a great flavor-infused oil that you can use to drizzle on your pizzas or use as a base for your salad dressings.