There are various ways to deposit thixotropic pastes in a more or less controlled way; you can squeeze them out of a nozzle, RepRap-style, or form them with a spatula like cake icing, or stamp them between dies, or imprint their surface with dies such as Sumerian rollable clay seals, or cut them with blades. These techniques have been central to human manufacturing since the Neolithic advent of pottery; clay bodies have the desirable trait of having an extremely small elastic deformation limit beyond which they deform plastically, permitting fairly precise dimensional control of the result, though this is often compromised by the grain size of tempers in the clay body and by contraction on drying.
Often dimensional precision is compromised by adhesion to the tools being used, but a spritz of liquid mold release or coating of solid powder is frequently sufficient to keep this source of error manageable. In other cases, a layer of rapidly flowing gas or liquid, as in an air bearing or air-hockey table, may eliminate this problem.
It occurred to me today as I was watching peaks of dulce de leche stubbornly fail to collapse that emulsions like mayonnaise and dulce de leche are generally thixotropic, as are liquid-gas foams. I guess the energy to deform droplets of the discontinuous phase out of sphericity manifests as enough elasticity to render the overall metamaterial thixotropic.
[Later I read some papers about dulce de leche rheology, and that’s not why it’s thixotropic. It's thixotropic because the sugars and polysaccharides form a gel.]
If the thixotropic paste is sufficiently dimensionally stable, this is the easiest way to realize arbitrary high-precision three-dimensional geometry. Often, though, the thixotropic substance itself doesn’t have the desired properties; mayonnaise, for example, noticeably lacks structural strength.
[Note that the above uses the wrong definition of thixotropy: I thought thixotropy was the phenomenon where viscosity increases instantaneously at low shear rates, but actually thixotropy is where viscosity increases progressively over time at low shear rates, which is a phenomenon that does happen with dulce de leche.]