F-150 here. Two to four tie down staps works well, but with a tool box you have to turn the front wheel to get it in. I don't really like just laying my bike in the back to scoot around, even with a bed liner.

For less than $100 (if you have a receiver hitch) U-Haul has a really cheap and simple rack that folds up over the tailgate when not in use and will haul 3 bikes. You will, however, need bungie cords to immobilize the bikes as the rack just supports them by the top tube.