The best way to free you smartphone from using cases is to use bumpies - in order to keep your S5 thin, fast accessible and small enough to be worn/kept on almost clothes and bags.
There is used a technology called ProDyn impact dissipating, that have the major role to protect your S5 against almost all drops on flat surfaces. These bumpies can be very easy installed on your device - it's not complicated. Also, related to bumpies exists a little problem: the access to your S5 battery will be blocked, but usually is no reason to remove your battery from your smartphone, except the service maintainance cases that can happen one time in a few years...
Where to get Bumpies for Galaxy S5?
On the internet are many websites that sell bumpies, but cheapest and high quality products can be found here!