99 cents via eBay offers the Sticky Pad Anti-Slip Mat for $2.99 with free shipping. That's the lowest total price we've seen for an anti-slip mat with a "v slot", and a current per-unit price low by at least $1. The "v slot" holds most cell phones upright in landscape mode.
Allow two to three weeks for this item to arrive.
Part-time and remote gigs offer a host of perks for various types of workers, but finding them can be overwhelming. Start with this list.