Preheat the oven to 350 degrees F. Grease a 9-by-13-inch pan.
For the dough: Scald the milk. In a stand mixer with the dough attachment, combine the salt, butter and 1/2 cup granulated sugar. Add the scalded milk. Add the eggs and vanilla and mix until combined.
In a separate bowl, add the yeast to the hot water with 1 teaspoon granulated sugar. Let the yeast mixture sit for 3 minutes to make sure the yeast activates. It should foam and start to bubble.
Add the yeast mixture to the mixer. Add 4 cups flour and Clear Jel Instant, if using, to the mixer. Mix on low speed for 3 minutes. If the dough is too sticky, add flour in 1/4-cup increments, using no more than 5 cups of flour total.
Let the dough rise in the mixer bowl until it doubles in size, 1 to 1 1/2 hours. Punch down the dough. Roll out on a floured surface to a 12-by-8-inch rectangle.
For the filling: Spread the melted butter on the rolled-out dough.
In a bowl, combine the brown sugar, cinnamon and salt. Spread the filling mixture on top of the buttered dough. Lightly dust with 1 teaspoon flour.
Roll the dough into a log. Cut the log into 8 pieces. Place in the prepared pan. Let the dough rise again until it doubles, 1 to 1 1/2 hours. Bake until golden brown, 20 to 30 minutes.
For the glaze: Mix the confectioners' sugar, maple extract and milk in a bowl.
Allow the cinnamon rolls to cool a bit, then drizzle with the glaze.