The lock side is great, however, shoes does not stay on the platform side. Your leg always slip out from the pedals during pedaling. Any solution to improve it?
Some people have modded the pedals to add set-screws which provide better grip. Typically this involves drilling a hole, tapping it for threads, and adding a set screw of the desired length.
For example, here's an a530 with 2x set screws added:
I would pay a visit to your local skateboard shop and get some 'skateboard grip tape'.
This should be inexpensive and it can be applied in such a way that your pedals are not permanently damaged. The glue on the stuff is pretty good and it is pretty much totally designed for keeping feet in place.
Your pedals might look a bit naff with bits of tape wrapped around them, a further consideration is that you could go away from the normal black and get hi-viz tape.
I wired a piece of rubber tubing around the front and back beams on mine and it helped a lot. I like the skateboard tape idea and will try it. These pedals are beautifully finished but the edges of all the lugs are rounded over and then hardcoat anodized resulting in a really slippery pedal; your feet tend to slide sideways and go off the outside edge periodically. Wearing SPD MTB shoes on the flat side is the worst, especially when the cleat reaches the outside edge. Running shoes are definitely better. None of this has anything to do with technique; I have old style metal and rubber pedals that you slide off of if you hit a large bump, otherwise you're fine, but these are slippery enough that you can nail your ankle pretty easily. There are a bunch of pedals like the mentioned Shimano M 324 that I think should be better, mostly at the expense of increaded wieght.
I'm not sure there is a good answer to this question. It probably depends most on what type of shoes you wear. Have you tried using trainers/sneakers with a rubber sole? I wouldn't want to try and modify the pedals as you may risk damaging them.
If you want a really good reliable pedal connection on the platform side, I reckon the Shimano M324 pedals are more likely to suit.
Perhaps you need to change your pedalling style when you're riding without clips: push (only) down onto the pedal, instead of spinning.
That's why you have clips.
This seems an easy solution pretty easy to take on and off: