Start by finely chopping garlic
Sprinkle with salt. The salt acts as an abrasive and also pulls moisture from the garlic to help create a paste
Start by pressing down on garlic with the side of your blade and scraping across.
Continue pressing and pulling blade over garlic pile
Garlic will begin to release moisture and start looking like a paste. Add more salt as needed
Continue pressing and pulling with blade until get the constancy you're looking for :)