Preheat the oven to 375 degrees. Line a baking sheet with tinfoil.
Slice the mushrooms then place them in a single layer on the baking sheet. Drizzle with olive oil then toss to coat evenly. Season with sea salt and freshly cracked pepper, to taste along with some fresh thyme then toss to coat again. Place into the oven and roast, stirring halfway through, for 17-20 minutes. Remove the mushrooms from the baking tray and set aside.
Turn the oven to broil. Place the toast on the same baking tray you cooked the mushrooms on. Place under the broiler to toast making sure to watch carefully so they don't burn. Flip and toast the other side. Remove from the oven and rub both sides of each piece of toast with a clove of garlic. Divide the toast evenly with the mushrooms then top with grated Swiss cheese and fresh thyme. Place back under the broiler, making sure to watch carefully so they don't burn, until the cheese melts.
Remove from the oven and serve immediately. Enjoy.