Whisk lemon juice, lemon zest, honey, Dijon, olive oil, salt, pepper, and red pepper flakes until glossy and emulsified.
Slice cucumbers and red onion thinly; shred the carrots.
Combine cucumbers, carrots, and onion in a large bowl.
Pour the vinaigrette over the vegetables and toss to coat evenly.
Fold in the dill, then taste and adjust seasoning if needed.
Chill 10 minutes for flavors to meld. Add almonds just before serving.