Line a 7x11" glass baking pan with parchment paper.
In a large mixing bowl, combine the trail mix, whole oats, oat flour, chia seeds, and salt. Stir until combined.
NOTE: If your trail mix contains chocolate, place the mixture in the freeze while you make the peanut butter mixture. This will help prevent the chocolate from melting too much.
In a medium saucepan over medium heat, combine the honey, butter, and peanut butter. Stir until the butter is melted and the mixture is smooth and creamy. NOTE: You could also heat the mixture in a microwave-safe bowl in 15 sec. increments.
NOTE: If your trail mix contains chocolate, let the peanut butter mixture cool for 10-15 minutes before stirring it into the trail mix mixture.
Pour the peanut butter mixture into the mixing bowl that contains the trail mix. Stir until everything is well combined.
Spread the mixture into the 9x11" baking pan. Pat it into an even layer. Allow the bars to set up at room temperature for at least 4 hours before transferring them to the fridge to firm up even more.
Once the bars have firmed up in the fridge, they will be easier to cut into granola bars and can then be stored in the fridge or at room temperature.