YBa2Cu3O6+δ microcrystals are synthesized by extraction of a nonstoichiometric melt similar to that employed for crystal growth of this compound. This method uses, first, initial compositions corresponding to the field YBa2Cu3O6+δ plus liquid, and second, the interaction properties of the flux with an appropriate substrate, i.e., Y2O3. Using other substrates like alumina produces 123 microcrystals, but embedded in the residual flux; in contrast yttrium oxide reacts with this one, and it is essential for its extraction. Choosing proper conditions makes it possible to obtain relatively pure YBa2Cu3O6+δ samples made of regular pellets (size: 10 to 20 μm thickness: 3 to 6 μm). The process is discussed using the phase diagram and the concept of dissolution-reprecipitation often involved in liquid phase sintering.