Final answer:
Bosnia-Herzegovina contains the most significant population of Slavic Muslims, where the Bosniaks reside.
Step-by-step explanation:
The country that contains Slavic Muslims is Bosnia-Herzegovina. This nation is located in the Balkans and formed after the breakup of Yugoslavia in the early 1990s. The Bosniaks, or Bosnian Muslims, are the largest group of Slavic Muslims in the region, having their own unique identity shaped by both their Slavic heritage and Islamic faith. The dissolution of Yugoslavia and the subsequent civil war were significantly influenced by religious and ethnic differences, with the Bosniaks inhabiting areas of former Yugoslavia that are now recognized as Bosnia-Herzegovina.