Pound the shrimp in a mortar and pestle or finely chop then set aside.
Slice the cucumber into batons or thick slices on an angle. Toss the cucumber in the salt, leave for 10 minutes then rinse, drain and place in a mixing bowl along with the shallot, sambal, salt, lime, sugar and dried shrimp.
Mix well then add the avocado and mix again.
Serve straight away with steamed rice.