From Ground: Firstly, water the quince plant thoroughly to soften the soil. Then, using your shovel or spade, dig in a circle around the plant, roughly 12-20 inches away from the base. The aim is to keep a substantial amount of the root system intact. Gradually work the spade under the root ball, lifting the plant out of the ground and taking as much soil with it as possible.
From Pot: Before removing the quince plant from its pot, water it well. Tip the pot sideways and tap the bottom to loosen it. Gently pull the plant out by grabbing the base. If it doesn't come out easily, you may need to break or cut the pot.
From Seedling Tray: Make sure the quince seedlings are well-watered. Turn the tray upside down and gently tap the bottom. The seedlings should fall out with the soil and root system intact. Handle the seedlings by the leaves, not the stem, to avoid damage.