Position the device such that the game cartridge slot is located at the top.

Locate the IR board located on the upper right side of the motherboard.

The IR board is installed upside-down in these photos by mistake. Installing it this way will result in your DS failing to start. Note the orientation of your IR board before you remove it, and reinstall it the same way.

Remove the IR board with a plastic opening tool by inserting the tool below the IR board and gently prying up.