Built one with no plan in the shape of a Chinese junk. Made one mistake -- too small. My first kid was born over 10lbs and he was 2 weeks premee. He out grew that cradle in 4 months. I saved that for my second child-- he refused to lay down in it-- he wanted to be hold in arms.
Well, I finally donated the cradle to the locate Mother and Child Center at the hospital run by the Cathlic nuns. They were totally serprised when I brought that in. When I talked to them on phone that I was going to donate a rocking cradle, they thought it was a mass produced store-bought cradle. You should see their eye popped. What could I do, I was going to move.
Anyway, I finished the cradle with many coats of hand-rubbed natural Danish oil, and the bottom got additional apar varnish (just in case the kid decided to leak in the middle of the night.) I read that Danish oil is non toxic after it cured. Good that it wass non toxic because my older son was born with a tooth and he really chew up the inwale. I sand and refinished the damaged part before I donated it.
I used yellow birch for the boat and oak for runners. It came out pretty nice.