Preheat your grill or campfire to medium-high heat.
On each foil sheet, place a salmon fillet in the center.
Surround it with a quarter of the asparagus.
Drizzle each salmon fillet with 1 tablespoon of olive oil.
Sprinkle the minced garlic evenly over the fillets and asparagus.
Season each packet with salt, pepper, thyme, and rosemary.
Top each salmon fillet with a few lemon slices.
Fold the foil over the salmon and asparagus, sealing all edges to create a packet.
Place the foil packets on the grill or over the campfire.
Cook for about 15-20 minutes, or until the salmon is cooked through and the asparagus is tender.
Carefully open the foil packets (watch out for the steam), and serve immediately.