Put the garlic, olive oil, mustard, honey, salt, pepper and rosemary in a Ziploc bag and squeeze to combine.
Add the chicken and then chill it for up to 24 hours (minimum 1 hour).
Get the grill medium-high, or at least 350 to 400 degrees F (180 to 200 degrees C).
Discard the marinade from the chicken.
Grill the chicken for about 6 minutes on each side or until cooked through, with the grill lid down.
Put it on aluminum foil and squeeze the lemon juice over it, then fold the foil all around the chicken.
Let it stand for 10 minutes before serving.
As boneless skinless chicken thigh recipes go, this one seems to appeal to just about everyone.