Candied honey studded with pumpkin, sunflower, sesame, and poppy seeds make up these sweet-and-salty bars.
Heat a large skillet over medium-high; add pepitas and cook, shaking skillet constantly, until darkened and beginning to pop, about 2 minutes. Transfer to a plate. Add sunflower seeds to skillet and cook, shaking constantly, until golden and beginning to pop, about 1 minute. Transfer to plate with pepitas; let cool.
Reduce heat to medium. Add sesame seeds to skillet and cook, shaking constantly, until golden, about 1 minute. Transfer to plate; let cool completely. Add poppy seeds to plate; stir to combine.
Coat a 12-by-17-inch rimmed baking sheet with cooking spray. In a medium saucepan, bring sugar, honey, and 1/3 cup water to a boil over high, stirring until sugar and honey are dissolved. Reduce heat to medium-high and boil, without stirring, until a candy thermometer registers 300 degrees. Remove from heat, add baking soda, and whisk vigorously just until incorporated, 2 to 3 seconds.
Pour mixture onto prepared baking sheet (do not spread; it will flow out to fill sheet). Immediately sprinkle with seed mixture and flaky salt. Let cool completely. Break into pieces; serve. Brittle can be stored in an airtight container up to 1 week.