last step, never wise to have live wires dangling about!
Depending on how big it is my methode may work for you, I assemble every thing starting from the charge controler, I work my way out to the batteries, hook all that up, verify all my wiring, then close the breaker, programe charge controler.
wire my way out to the pannels, then wait till dusk then wire all my pannels up and conect/ leave breaker open till morning. Morning I check all my wiring all my connections and then toss on the breaker and smile as you tell the utilities to sod off and give em a 1 finger salute!
and then I check the whole system a third time to be sure of it
let the bank charge up with no loads, then do an equilize to innitialize the bank, then take sp measurments and such and off ya go.