Base skills are technically anything apart of a creature's Essence and require no training, and therefore, creatures are considered at a Minor level of training, and do not start at a Flawed training level.
Meaning, that a creature starts off rolling one d20 as the Main Roll, and NOT at a Disadvantage Stack.
They are typically: Attention, Balance, Empathy, Endurance, Frighten, Influence, Initiative, Inspection, and Sneak.