Among the many traditions of bowl carving is the Yup’ik method of bending a separate length of wood that attaches to the hollowed base and serves as a higher rim. The interaction between material, hands, eyes — and teeth — to create the form and a tight connection is simply wonderful. I stumbled onto the short video above that features Yup’ik traditional scholars sharing memories of how these objects were made. The video also includes some close ups of the bowls.
I’m still pretty clueless, but one thing I notice is the thickening of the rims along the straighter portions of the bowl. Seems to me that the wood has been made thinner where they want a tighter bend and vice versa. This would facilitate controlling the curvature at various points along the rim while bending without a form. Much to learn just from the short video and the accompanying information, drawings, and photos at this website through the Smithsonian Institution.