Slavonia rhymes with:
slovonia, slovonia, slovonia, slovonia, adonia, amazonia, ansonia, antonia, caledonia, colonia, cydonia, diaphonia, donia, estonia, gastonia, gonia, harmonia, idonia, latonia, macedonia, madonia, new-caledonia, omonia, patagonia, petronia, philharmonia, rondonia, sidonia, sinfonia, slovonia, sophronia, tonia, vernonia, vidonia
Slavonia sounds like:
salvina, salvino, schlobohm, sclafani, silvana, slaven, slavin, slepian, sleven, slevin, slip-on, slovene, slovenia, slovenian, slovonia, sullivan, sylvain, sylvan, sylvana, sylvania