What is best way to set up a defense?

If you want to defend against resource grabs only, keep the resources below the store limit. If you want to defend from warship losses at wartime, make sure you empty your base of as much warships as possible. Send as reinforcement to shielded bases, then put on carriers and anchor these carriers at a remote location to hide them. If your resources are above store limit, defend by putting a strong carrier with strong planes as your defense fleet. Put T1 ships on defense. If resources are below storehouse limit, defend by putting weak carrier with strong planes and T1 on defense.