(Optional step) Place finely diced (or grated) cucumber in a sieve over a bowl and sprinkle with 1.5 tsp salt. Stir and let sit for 20 minutes or so. Press the water out of the cucumber with the back of a spoon and shake the sieve to release the water. If you do this step, you'll likely not need to add salt later on.
Combine cucumber with the rest of the ingredients and place in the fridge till ready to serve.
Note: the garlic will "flower" over time and the flavor will be much stronger the next day. I recommend serving to guests the day it's made, and staying away from friends if eating it the next day ;)