hardcore survival: base layout and first week priorities

i just started a new hardcore world and want to get the early game right. i usually dig straight down for iron but that feels risky now. what is your go to first week routine. do you focus on food or shelter first.

i am also thinking about base placement. i want something defensible but easy to expand. are you building underground or on a cliff side. share your current setup and any tips for staying alive past day one.