Preheat your grill or a grill pan over medium-high heat. If using a grill, lightly oil the grates to prevent sticking.
In a small bowl, whisk together the honey, pineapple juice, soy sauce, olive oil, minced garlic, and ground ginger until well combined.
Season the salmon fillets with salt and pepper on both sides.
Place the salmon fillets in a shallow dish and pour half of the honey-pineapple mixture over them, reserving the other half for later. Let the salmon marinate for about 15-20 minutes.
If using fresh pineapple slices, brush them lightly with olive oil and set aside.
Remove the salmon from the marinade and place it on the grill. Cook for 4-5 minutes on each side, basting with the reserved honey-pineapple mixture during the last few minutes of cooking. If using pineapple slices, grill them for about 2-3 minutes on each side until grill marks appear.
Once the salmon is cooked through and flakes easily with a fork, remove it from the grill and let it rest for a couple of minutes.
Serve the salmon garnished with chopped green onions and grilled pineapple slices, if desired.