Yes you can get the shape you want by steaming, tying, setting aside for a day then drying in an oven or using a microwave to get the excess water out.
The amount of bend possible is of course dictated by thickness, grain and flexibility of the wood.
This is the point I made about Jeorg's Phoenix slingshot being made from a tree branch that didn't match the desired shape.

 

Ok, thanks. Is there a proper method for steaming or can you just boil a pan of water and place the fork above it?

 

There are different ways of steaming the wood but you can just boil it and it will work fine

 

if you make a tent out of aluminum foil above the pot and use a wire mesh or something to hold the slingshot in the steam that would work well. a boiling pot and aluminum tent are all i use when recurving bows.

 

Ok, thanks Gopher. That's a very useful tip

 

Gopher, thanks for a good tip.

Also I learned from Fish that you can toss it in a pressure cooker for 20 minutes or so to soften it up.