Positive representations, defined by Fock and Goncharov in 2003, are a class of interesting representations of the fundamental group of a surface with non-empty boundary into PSL(n,R). Under some additional assumptions, these representations are B-Anosov, and so by results of Guichard-Wienhard and Kapovich-Leeb-Porti, they admit cocompact domains of discontinuity in projective space when n is even. I will explain how to build polyhedral fundamental domains for this cocompact action, and for n=4k+3. I will explain how a similar construction gives a compact fundamental domain in the sphere S2k+2. This is joint work with N. Treib.