Preheat the oven to 350° and line a baking sheet with parchment paper. Spread the pecans, oats, pumpkin seeds and flaxseeds on the sheet and bake until fragrant, 8 minutes. Transfer the mixture to a large bowl.
In a saucepan, bring the sugar, honey, butter and salt to a boil over moderate heat. Simmer until the sugar is dissolved and a light brown caramel forms, 5 minutes. Remove from the heat and stir in the vanilla.
Drizzle the caramel all over the nut-and-oat mixture. Stir in the puffed rice and cranberries until evenly coated.
Line an 8-inch square baking dish with parchment paper, extending the paper over the side. Scrape the cereal mixture into the dish in an even layer. Cover the mixture with a second sheet of parchment and press down to compress it. Let stand until firm, about 2 hours.
Discard the top piece of parchment. Using the overhanging paper, lift out the cereal square and transfer it to a work surface. Cut into 12 bars and serve.