Ollas (pronounced “oy-yahs”) are unglazed clay/terra-cotta pots with a bottle or tapered shape that are buried in the ground with the top/neck exposed above the soil surface and filled with water for sub-surface irrigation of plants.llas in Sri Lanka Photo copyright © Craig Mackintosh. “Maria created her highly prized black pots by using the bottom of an old plate (puki)… Beginning by patting a tortilla shaped piece of clay in the puki, Maria then rolled a lump of clay between her palms, creating a long clay rope of uniform thickness.