Clipping in to single-sided pedals can be a complete nightmare on steep climbs. This kind of thing ...
And putting a foot down on such evil slopes can be equally dodgy, as I discovered a few seconds before taking that photo!
My Cannondale had Look pedals on it then so my shoes had slippery plastic cleats attached to the soles. I had to do an emergency dismount when my legs failed me on that 25% slope and my foot slid from under me, almost causing me to faceplant on the road!
I took the photo and then attempted to have a second go at the climb. I failed to clip in and had another go at kissing the tarmac. At that point, I decided to walk up round the bend at the top where the gradient eased ...
The 3rd thing wrong with single-sided (non mountain bike type SPD) pedals and the corresponding plastic-cleated soles is that it is incredibly difficult to walk up steep hills on them!
After my 3rd, 4th and 5th attempts at face-tarmac interfacing, I decided to switch the bike back to my trusty Shimano M520 SPDs. No more such problems.
If you stick to single-siders with their dodgy cleats and you ever have to start off up a steep slope like that, see if you can emerge from a side road, farm track etc. That gives you a chance to clip in before turning up the slope. If there isn't anywhere suitable to do that and the road is wide enough, wait until there is no traffic and clip in riding across the width of the road, then turn up. A final option is to hang on to something at the side of the road (a handy wall, fence, bush, whatever ...) and clip BOTH feet in before setting off! NB - engage your lowest gear before setting off - you will come to an immediate stop and fall over if you are in too high a gear!