If I’m in the aisle I leave my bag in front of my seat until my window seat mate boards. If they are not using the middle, I use it but cram my bag close to my side so they can put their feet on their half. If they need it I shove my bag in the bin after everyone in F has boarded. If I’m in the window I pretty much do the same thing except ask if I can use that space for my bag. If they object which has never happened I would put my bag in the bin and take it down using a bit of a slow walk.