There is basically no right or wrong way to mount a Saphe One and Saphe One+.
We recommend that you are mounting it so you can clearly see it and reach the buttons on it.
Our recommendations are either in the windshield or on the dashboard, and if you mount it vertically we recommend that the buttons face upwards.
On the backside of the Saphe One / Saphe One+, there are some adhesive pads to mount it with.
Here is a small video of how to mount them: