Clay is usually found near moist areas as the silicate is usually the product of natural conditions near waterways and bodies of water. Ideally, it should be on land adjacent to water, but since that's not possible, clay deposits in shallows is the best we'll get...
As to 'how you get it', it's not a strategic resource, it's a bonus resource like whales and fish, and hence simply needs to be within the city radios. Note - you gotta have Pottery for it to be visible...
Clay is not found on most plains - it's found where water and hydro action is, or was (clay layers where land was once covered with water, etc.). Clay is often found in river deltas and riverbanks as sedimentary clay accumulates there. Additionally, in salty areas such as marshes and coastal areas and river deltas, where brackish waters are found, clay accumulates due to how clay behaves in areas of high salinity. Clay hence was harvested in these areas, and that's why it appears adjacent to the coast - cause that's most often where they got it!
Venger
As to 'how you get it', it's not a strategic resource, it's a bonus resource like whales and fish, and hence simply needs to be within the city radios. Note - you gotta have Pottery for it to be visible...
Clay is not found on most plains - it's found where water and hydro action is, or was (clay layers where land was once covered with water, etc.). Clay is often found in river deltas and riverbanks as sedimentary clay accumulates there. Additionally, in salty areas such as marshes and coastal areas and river deltas, where brackish waters are found, clay accumulates due to how clay behaves in areas of high salinity. Clay hence was harvested in these areas, and that's why it appears adjacent to the coast - cause that's most often where they got it!
Venger