I'm happy with the Mophie wireless charging base. It has 7.5W fast-charging speeds and it's a non-slip surface. Kind of rubberized so the iPhone stays in place.

http://www.mophie.com/shop/wireless-charging-base

$22.99 on Amazon Prime right now -

https://www.amazon.com/mophie-Wireless-Charge-Optimized-Technology/dp/B075M4ZH17/ref=sr_1_3?ie=UTF8&qid=1544218575&sr=8-3&keywords=mope+wireless+charging+base