Drain the chickpeas reserving some of the liquid for later. Put the chickpeas is a sturdy bowl, add the salt, chili powder, coriander powder and the olive oil and then mash them with a potato masher until they are fairly smooth but retain some texture. Don't simply blitz them into a paste. Texure is interesting! If it is too stiff or dry to work with add a little of the reserved fluid drained from the tins. But go easy it needs to line the flan dishes. A tablespoon ought to be enough.