1. Ko Soto Gake is basically the 'hooking' version of Ko-soto-gari. Your toes need to be pointed, creating a 'hook' with your heel and ankle which you then hook around your partners ankle dragging forward for a banana-skin effect.
Your hands are important with this technique as your hike-te needs to be pulling downwards whilst your tsuri-te needs to be directing your partners balance correctly.
2. Second version, more of a wrap around the leg, same action with your hands, but your leg needs to hug the leg - as shown in the below video:
