I know this is an older thread but I thought I would add a method to use shorter lengths of rattan for a handle.
This the method I use on fly rod cork grips.
If I know I will need to use two lengths of rattan, I make sure the splice is half way up the handle, just for visual appeal.
Drill a small hole, the same size or slightly smaller than two strips of your rattan. Put super glue in the hole and insert the ends of boths pieces.
Now start your wraps from there, working your way up and down. It is much more difficult to start at one end and try to splice as you go.
If done correctly the splice is barely noticeable.
Patrick