There are two ways to go about this (assuming you want to make the pattern from wood): cut it out of a single block, or glue it up from separate parts. I chose the former, because it seemed easier to me after taking stock of my selection of stock. You can do it the other way, it would be the easier of the two options, providing you had stock of the right dimensions handy.
Anyway, here are some photos of it, and here is a link to a pdf with the cutting sequence I used. I hope it makes sense, if not, let me know.
The top of the carriage
And the bottom
Obviously the pattern isn't completely done, I need to finish plugging little holes in the surface, give it a good sand, and paint it with something glossy. But it has all its tapers and rounded edges.