From Ground: First, water the sea lettuce plant to dampen the soil. Then, using a shovel or spade, dig around the plant, ensuring the plant's root ball remains intact. Carefully place the spade under the root ball and lift the plant from its original location.
From Pot: Begin by watering sea lettuce adequately. Later, tip the pot sideways while gently holding your plant at the base it should slide out. If the plant resists, you might need to tap the pot's bottom or rim.
From Seedling Tray: Water the seedlings adequately. Then, when you're ready to transplant, push the seedling out from the bottom carefully. Ensure you're not pulling the plant as it might damage the tender roots. Better still, use a spoon or trowel to gently coax it out.