when to start lst

this is my first grow and its barely starting to sprout i want the plant to be short and fat and i heard LST is perfect for what i want but how do i do it and more importantly when
also im going to do the uncle bens topping method so whould i start LST after i do the uncle bens topping

i'd start at 6 or 7 inches tall, before the stem hardens and is more vulnerable to snap.