1. Preheat oven to 400°.
2. Put potatoes in a medium pot with enough water to just cover them. Cover pot and bring to a boil, then lower to a simmer and cook until potatoes are tender, 15 to 20 minutes. Drain. When cool enough to handle, peel if you like and cut into wedges.
3. Meanwhile, separate garlic head into cloves, then peel cloves. Add to a large frying pan with onions and oil and cook over medium-low heat, covered and stirring occasionally, until garlic is soft and just starting to turn golden, 10 minutes.
4. Add the potato wedges and 1/2 tsp. salt. Cook, stirring frequently, until the potatoes are golden brown, about 10 minutes. Add red pepper and cook to heat through. Taste the mixture and season with salt if you like.
5. While potatoes brown, arrange meats, baguette slices, and olives on plates or on a single platter to share.
6. Put a heavy 10-in. cast-iron or enameled cast-iron frying pan in oven to warm 5 minutes (cast iron holds heat well and will keep cheese oozy longer). Add raclette to pan and cook until cheese is hot and evenly melted, 5 minutes.
7. While cheese melts, set everything on the table, including a trivet or warmer for the hot cheese. When cheese is ready, slide it to one side of pan by tilting pan. Transfer potato mixture to cleared side of pan and tuck thyme sprigs next to it if you like. Serve immediately.
*Find raclette at well-stocked grocery-store cheese counters and at cheese shops. If you're using gruyère, a less heat-tolerant cheese, toss it with 1 tbsp. cornstarch and soften it over very low heat on the stovetop, until almost melted; then remove from heat and stir.