Ritual of Summoning.

Just move yur warlock and 2 other guys to wherever you want to go.

Move forward to the outer edge as stated, then back up yur main hugging the outer edge so your followers clear whatever is obsturcting them, then slowly move forward, again at the outer edge. Ya move, stop, move, stop etc. so that they clear the center area (i.e. the center is not between the lead and followers). As long as the center is never between leader and followers you never stick.

But a warlock gonna save you a tons of time.