A short opening list is easier to follow than a rigid minute-by-minute script. Secure a fallback, lock a starter, then build the resource loop that supports the next move.
Secure a return point
Place sleeping bags along the route and keep one fallback away from the planned base area.
Lock the minimum base
An airlock, tool cupboard, storage, and a furnace are enough to protect the first useful haul.
Upgrade the obvious weakness
Replace the starter entrance before spending the same resources on a larger but poorly secured shell.