In the beginning most beginners feet are not very flexible. With time your feet will become more relaxed and flexible and the pocked will fit fine.
About the sliding blade, it's a matter of technique and practice.
Mostlikely you're flexibility is limiting your ability to gradually build up pressure on the fin's blade whilst maintaining stability.
Back, belly strenght and flexibility and coordination are what beginners are seeking
Another idea for building those is:
On the back, on the surface, wearing normal scuba fins, arms overhead carrying a 1KG weight swimming lanes. I like to swim about 1km this way, where I have a incremental increase in intensity ending in 4x50m sprinting. After this I need some recovering breathing and than feel much more flexible. Than I'll put on my dear 'Natalia' and dance the gracious glide dance
In general, learning monofinnin needs a searching mind with discipline to swim long distances to anker movement, increase flex, stamina and strength.
Kars
