From Ground: Start by watering the soil around the camphorweed plant to make it easier to remove. Then, using a shovel or garden spade, dig around the outer edge of the plant's root zone. The goal is to minimize root damage, so make sure you're digging wide enough. Once done, carefully put your spade under the plant and lift it out from the ground.
From Pot: First, water the plant in the pot to let the roots absorb moisture. Then, tip the pot sideways and gently tap it to loosen the plant. Be careful not to pull the plant, it should easily slide out with a little coaxing.
From Seedling Tray: Water the tray first to moisten the soil. Using a garden trowel or a spoon, gently dig around each camphorweed seedling to lift it out, making sure you've got as many roots as possible without causing damage.