I designed and sell a bag here that fits under the large side of the seat and leaves the small seat open on the side. Let me know if you have any questions!

Use this $30 OFF ☆ PROMO CODE:30STORAGE to get OEDRO bin for your F150.

Got this https://www.lowes.com/pd/AWP-Polyest...l-Bag/50175657 set of bags at Lowes. Super cheap and work great. One holds all my straps and the other holds a simple set of hand tools. I have a few of these https://www.lowes.com/pd/AWP-Polyest...l-Bag/50175657 bags from Harbor freight. Again, affordable and hold up well. All of these bags are also small enough to fit behind the seat back.

I have had the exact same bags for a few years, they work great. I have a few tools, straps, bungees and a small chain in mine. they hang perfectly from the box link tie downs in the back too. keeps them out of the way are from sliding around. Just don't hang them if they are heavy, might tear the straps, don't ask me how I know!

https://cimg9.ibsrv.net/gimg/www.f15...8d0045e19.jpeg