An Aukey air vent magnetic car mount is down to $6.88 with code AUKEYC38 on Amazon. This mount is normally $13 and only drops this low through the occasional coupon code.
That mount is best for phones around the size and weight of the iPhone 7. If you need something bigger for a phone like the iPhone X, this similar air vent car mount is down to $5.99 with code AUKEYHC5. It sells for $8 without a coupon code.
These car mounts easy secure to one of the air conditioner vents in your car. You then put one of the included magnetic plates between your phone and a case, and you can easily place and remove your phone on the mount. Because there are only magnets holding the phone to the mount, you can rotate it to any angle and easily switch between landscape and portrait mode.
All Aukey products are backed by a two-year warranty.