In a small saucepan over medium heat, add olive oil. When the oil is shimmering, add the minced garlic and chopped fresh rosemary. Sauté until fragrant and the garlic is just starting to color.
Add 1 cup of water and ¾ tsp of Diamond Krystal kosher salt.
Little by little to prevent lumps, slowly whisk in the chickpea flour. Once all of the flour has been added, lower the heat to medium-low and continue whisking vigorously, until the mixture is thick (similar to polenta) and starts to pull away from the edges of the saucepan.
In an even layer, spread the mixture into a pan or container, or onto baking sheet about ½ inch thick. I used a 9x6 inch pan (See Note 1). Let cool for at least 1 hour until firmed up.
Preheat the oven to about 140℉.
When you're ready to fry the panelle, heat about ½ inch of vegetable oil to 350℉ in a frying pan. Keep the heat between medium-low and medium.
Cut the cooled panelle into 2½ x 1½ inch rectangles.
Fry the panelle rectangles in batches (don't overcrowd the oil) for about 3 minutes on each side, until golden brown. Remove and drain on paper towels. Season with salt while warm, then place into the warmed oven while you finish frying the other panelle rectangles.
Warm the pitas and carefully split open the pockets. Spread a decent amount of mayonnaise inside of each pocket, then stuff each pita with an equal amount of fried panelle and fennel slaw. Serve with lemon wedges to squeeze over top.