  The presence of electric or microwave fields can modify the long-range forces
between ultracold dipolar molecules in such a way as to engineer weakly-bound
states of molecule pairs. These so-called field-linked states [Avdeenkov et
al., Phys. Rev. Lett. 90, 043006 (2003), Lassabli\`ere et al., Phys. Rev. Lett.
121, 163402 (2018)], in which the separation between the two bound molecules
can be orders of magnitude larger than the molecules themselves, have been
observed as resonances in scattering experiments [Chen et al., Nature 614, 59
(2023)]. Here, we propose to use them as tools for the assembly of weakly-bound
tetramer molecules, by means of ramping an electric field, the electric-field
analog of magneto-association in atoms. This ability would present new
possibilities for constructing ultracold polyatomic molecules.
