You could also use this as a sandwich filling too!
Lightly coat a medium skillet with oil and heat over medium-high heat. Sear halibut steak until browned, 3 - 5 minutes per side. Allow halibut to cool, then flake into large pieces and set aside.
Mix together mayonnaise, celery, scallions, and dill in a medium bowl and season to taste with salt and pepper. Fold in flaked fish and adjust seasonings. Use as a sandwich filling or serve as a salad.