Begin by powering off your Nintendo 3DS XL completely. Flip the device over and use a Phillips screwdriver to remove the battery cover screws. Carefully take out the battery to ensure no power is running through the device during the repair.

Unscrew the remaining screws on the back of the 3DS XL using the Phillips screwdriver. Carefully use a plastic opening tool to gently pry off the back cover, exposing the internal components of the device.

Locate the cartridge slot assembly. You may need to remove additional screws or ribbon cables to gain full access. Use tweezers to carefully disconnect any cables attached to the cartridge slot, noting their original positions for reassembly.

Use a can of compressed air to blow out any dust or debris from the cartridge slot. If there are visible bent pins, use tweezers to gently realign them. A microfiber cloth can be used to clean the exterior of the slot.

Inspect the cartridge slot for any damage that cannot be fixed with cleaning or minor repairs. If necessary, replace it with a new cartridge slot. Ensure the new slot is properly aligned and secure it with screws.

Reconnect any ribbon cables and carefully reattach the back cover of the device. Secure all screws tightly, but avoid over-tightening to prevent stripping the threads.

Reinsert the battery and power on the device. Insert a game cartridge to test if the slot reads it correctly and ejects without issues. Perform several tests to ensure consistent performance.