Just a reminder - all capital letters on internet language means shouting. I know your frustrated but we can hear you well enough.
It is possible to move those 3 slabs to position - just takes patience and a lot of moving around:
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Stabilize the slab - Climb up the block podium on the left.
Climb and drop down behind the pink carved block (let's call it B) above the bottom carved block. Push the carved block over the other carved block (let's call it C). Push block B to the left part of the structure close to another carved block on top of the structure (let's call this one - A).
Move the bottom carved block C that is close to the slab and fit it on the space below the 2 carved blocks (A and B) on the left side of the structure.
Push the first moved block (B) to the niche to the right of the carved block (A) above.
Move the top carved block A to the right.
Pull the carved block B on the niche and move it to another niche by the moved top carved block A.
Place the lower carved block C that was moved on the left back to its original position.
Push the top carved block A to the right.
Move the middle carved block B back to its original position.
Now move the top carved block A to the left end of the slab to hold it in position.
Cross the slab and enter the opening on the wall.