Line an 8x8-inch baking pan with parchment paper, leaving extra on the sides to pull the bars out of the pan. For thinner granola bars, use a 13x9-inch baking dish.
Roughly chop the almonds and cashews, or pulse the nuts gently in a food processor or blender until medium-small pieces. Place the chopped nuts in a large bowl with the old fashioned oats, ground flax, mini chocolate chips, dried cranberries, and raisins. Mix together.
In a separate microwave safe bowl, melt the peanut butter. Stir in the honey and sea salt. Allow the mixture to cool slightly (so the chocolate chips won't melt). Pour the peanut butter mixture in the bowl with the dry ingredients. Fold ingredients together with a spatula until everything is coated.
Press mixture into the parchment lined baking dish, packing it tightly. Cover and refrigerate for at least 1 hour. Pull the granola slab out of the pan with the edges of the parchment paper. Cut into a minimum of 12 bars. These granola bars are best stored in an airtight container in the refrigerator up to 2 weeks. Optionally store in an airtight container at room temperature up to 10 days.