Arties is the best resource to keep an eye on for current info.
In my opinion there’s better walleye options in that region. You can catch them on big stone but it’s not where I’d go out there.
Id suggest going another hour west and focusing on the Webster SD area if walleyes are the main focus.
Big stone definitely has walleyes but not like it used to. As bass, bluegill, and crappie populations have increased the walleyes have gotten harder to find.
Traverse and LQP are both worth keeping in mind too.