A clay lamp makes a useful companion to a discussion of the five elements. You can point to the firm rim, the liquid oil, the flame, the moving air and the space around the wick. It is a teaching illustration, not an experiment claiming to have isolated five substances.
In Ayurvedic accounts the five great elements are earth, water, fire, air and space. They offer a vocabulary for thinking about qualities such as solidity, fluidity and movement. A student who meets the word earth in this context gains little by trying to find soil inside the body.
Try describing the lamp before and after it is lit. What moved? What held its shape? Which changes could you measure with instruments? The descriptions serve different purposes. Preserving that distinction helps an English reader understand a classical account on its own terms without turning the five elements into a rival periodic table.
Further reading: Indian perspectives on Ayurveda (NEIAH)