Heat a kadhai (pan) and roast jeera in it for 3-4 minutes, and then turn off heat.
Add black peppercorns in the kadhai and mix them with jeera using a spatula. (Make sure you're using a metal kadhai, as it will remain hot for a while even after turning off heat.)
Allow the jeera and peppercorns to cool, and then grind them to a powder using a mixer.
Now, add all the salts in the same pan and turn on heat.
Stir the salts on low heat for about a minute till the mixture is nice and dry.
Mix the salts, and the powdered jeera and black peppercorns.
Sieve the mixture onto a dry plate, and then store it in a dry and airtight container. (This masala lasts us for six months, you may want to reduce the quantity of ingredients proportionately if you want to make it in lesser quantity.)