The last 2x 00 philips screws are located under the L and R click buttons.

Do not remove the "Microsoft spine" piece. Instead move it aside to pop the buttons past it.

You might have to angle your screwdriver to get to the screws but this was not too difficult. I found it easier to come in from the middle.

The "Microsoft spine" is pressed into the button assembly using a one way barb as pictured. This would break if you try and take it off before removing the whole assembly.