Slice each piece of tofu crosswise into 4 (1/2-inch) thick slabs. Place a clean kitchen towel onto a rimmed baking sheet so that only half the towel is on the sheet. Put the tofu in one layer onto the towel and fold the other half of the towel over. Gently press the tofu several times to extract the excess water.
Mash the garlic to a paste with the salt. In a large bowl, whisk together the mint, lemon zest, lemon juice, garlic paste, and pepper flakes. Whisking constantly, drizzle in the olive oil.
Toss the tofu with the marinade, cover with plastic wrap, and let it sit at room temperature for 30 minutes, or refrigerate it for up to 12 hours.
When you are ready to cook, preheat a large cast iron skillet over medium-high heat for several minutes. Lift the tofu from the marinade, gently pat it dry with a paper towel, and place it in the pan. Reserve the marinade. Weight the tofu by placing a smaller pan with a clean bottom on top and weighting it down with a full tea kettle, a heavy can of tomatoes, or a clean brick. Cook for 5 minutes, then reduce the heat to medium and continue to cook until the tofu is well browned, about 5 more minutes. Flip the tofu over, put the weight back on top, and cook until the tofu is browned on the second side and cooked through, about 6 to 8 more minutes.
Transfer the tofu to a serving platter. Pour the oil out of the pan, then add the reserved marinade. Stir and simmer for 1 to 2 minutes, scraping up the browned bits from the bottom of the pan; pour over the tofu and serve.