A smooth resolution of singularities for a Schubert variety in a flag variety is constructed in terms of a Configurations variety directly obtained from its Relative Position Matrix. This is a canonical smooth resolution whose construction is suggested by our indexation of Schubert varieties in Flag varieties by Relative Position Matrices. We explicit a canonical decomposition of this variety as a sequence of locally trivial fibrations with Grassmannians as typical fibers. A schematic version of this construction is also given.