Here, we report a systematic method investigating how domains of interest can be localized at prescribed positions in many GUVs in a fluid environment. Our strategy consisted in confining vesicles in microfluidic channels to create free regions of curved membrane where the lipid phase in minority accumulated and formed a single domain minimizing line tension. GUVs of different Lo/Ld compositions were first confined in straight microchannels where we studied the spatio-temporal evolution of domain distribution. The analysis of hundreds of confined GUVs allowed us to establish the probability of having the minority phase in the prescribed free regions. This resulted in the formation of polarized GUVs having one or two Lo or Ld poles at its extremities, surrounding a confined body mainly composed of the other phase. Finally, other confinement geometries allowed us to direct the distribution of lipid domain into 3 or 4 well-positioned poles.