Since we are using fresh tamarind, which is very juicy and has seeds that won't come out very easily, you got to mash them well to remove the seeds. This is usually done using the mortal and pestle. You can continue getting a smooth consistency by grinding it and also adding the methi seeds along with salt.
Once the seeds are removed, you can further grind it smooth in a mixer or food processor. Then, the tamarind is stored along with the ground methi and salt for couple of days. Normally during the day, it is just left to dry in the shade.
When it is dried for couple days, you can season it and store it.
Grind the spices listed in the spice mix and keep it aside. This spices can be dry roasted and powdered.
Salt has to be mixed and mashed, only then the tamarind extract gets that typical taste. Adjust the spice accordingly. If you are using Green chilies, you need to add them while grinding in the mixer.