Pick basil leaves and place in a food processor or chopper. Add oil and salt and blitz until finely chopped. If you can’t fit it all at once, you can do one bunch at a time and divide the oil and salt between them.
Place heaped teaspoons into an ice cube tray. I use ice cube trays with silicone bottoms so the cubes pop out easily. Cover with plastic wrap and place in the freezer until set.
Pop out the cubes and place in a zip lock bag. Return to the freezer and grab a cube whenever you need one. 1 cube of basil paste should be close to 1 tbsp of chopped basil.