Mix the whole spices in a big plate and keep it in sunlight for 2-3 days. Turn over the spices sometimes when they are getting the sun light.Do not roast the spices while making garam masala just only sun dries them. If you do not have much time, then lightly dry roast the spices instead of sun drying them. Roasting too much will make your garam masala aromatic.
Mix all and grind it to fine powder and sieve it.
Store garam masala powder in an air-tight container for a year.