You need to bend the corners in the order: <span class='standouttext'>Spoiler : </span><span class='spoiler'>upper right, lower right, upper left, upper right again.</span> (highlight the text to read)
If you just want a hint, the end configuration is not a square with all corners touching, and you are not restricted to folding each corner once or required to fold every corner.
I don't recall if there were any clues for this, I just searched a walkthrough.
For the giant skeletons, you can defeat them through dialog, with either 16+ intelligence or a tomb about guardians and wards (which can be found on the first floor).
<span class='standouttext'>Spoiler : </span><span class='spoiler'>If you examine the guardians with a high intelligence you can read the symbols on their armour and find a way to disable them. With a lower intelligence you can use the tome of bone and ash (first floor, Zombie #732 at X=3760 Y=1920), which gives less experience. If you touch one of the skeleton guardians it will awaken and you will have to fight (this gives less experience than either dialog method).</span>
