OAST is an acronym for Old-fashioned Apple Slicing Tool, which is a traditional method of slicing apples into thin slices. The term OAST can be broken down into three crossword solutions: KILN (4 letters), OVEN (4 letters), and DRIER (5 letters). A KILN is a type of OVEN used to dry out the apple slices, while an OVEN is used to bake the slices until they are crispy. Finally, a DRIER is used to remove any remaining moisture from the slices. Together, these three pieces of equipment are used to create the traditional OAST slices.