Based on easts, new words formed by adding one letter at the beginning or end:
b - aesst c - basset d - bastes e - beasts f - castes g - stades h - steads i - tsades k - teases l - feasts m - sagest n - stages p - hastes r - siesta s - tassie t - skates u - stakes v - steaks w - leasts y - slates
