Take chillies in a bowl, pour boiling water over it and leave it aside for 10 mins.
Now drain them.
Take garlic and chillies in a blender and puree them using little of the drained water to a coarse or smooth mix.
Pour that in a bowl, add in salt and mix well.
Pour that in a freezer safe container and freeze.
Use as required.
Video
Notes
1)Since you are adding salt to the paste, you can easily scoop it even in their frozen stage, So you can use as per you need by scooping the paste using a spoon.2)This stays good more than a week in fridge and for more than 4 to 6 months in freezer.