Perhaps the problem is your ridiculous gearing. From what I can see in the picture, it looks like you're riding something like 52-16. If the gearing is too steep and you can't hold the skid, your foot will probably fall out.

A lot of things affect skidding. There's handlebars, body position, tires, terrain, etc. in addition to what's already been mentioned.

For now, I think you should work on your technique and get a brake.