Make vinaigrette: Whisk olive oil, lemon juice, honey, poppy seeds, and Dijon until emulsified. Season with a pinch of pepper. Divide among six small, leak-proof containers.
Toast pecans: Dry-toast over medium heat 3 to 5 minutes, tossing often, until fragrant. Cool completely, then roughly chop.
Season chicken: Pat dry. Mix herb blend, garlic powder, and black pepper. Season chicken evenly.
Cook chicken: Heat 1 tbsp olive oil in a large 12-inch skillet over medium-high heat. Cook 6 to 8 minutes per side until golden and the thickest part reaches 165°F 74°C.
Cool, rest, slice: Transfer to a plate, rest 10 minutes, then refrigerate uncovered until fully cool. Slice into thin strips.
Assemble: In six wide-mouth 32 oz 1 L jars, layer sliced chicken, chopped pecans, strawberries, goat cheese, then gently pack spinach on top.
Store and serve: Seal jars and refrigerate at or below 40°F 4°C for up to 4 days. Keep dressing containers chilled separately. To serve, pour dressing into the jar, seal, shake 15 seconds, and enjoy.