Since Level 4 seems to be the one where the Boring Stones are hardest to find, I decided to write a guide helping you to find each stone.
The Pyramid in Level 4 has 6 Stages (including the top where you fight Big), I will refer to them as Stage 1 to 6. To be clear about the four different sides of each stage, I refer to them as South, East, North and West.
The side you start on is South!
Also, I will not describe how to get to certain sides of the stages, but feel free to comment if you're stuck.
I numbered the stones in the order I collected them, which I find is the most direct one.

Stage 1:
South:
Stone 1 and 2: Inside the big doors you face right at the start.
Stone 3: On top of the right ramp leading to Stage 2.
Stone 4: A bit left over the first tape (right above the big door where the first two stones are in).

East:
Stone 5: On an island in the corner between East and North

North:
Stone 14: Right in the middle.

West:
Stone 13: Right in the middle.


Stage 2:
South:
Stone 6 and 7: Right in front of you and a bit to the left.
Stone 8: On top of the tower that stands in the southwest corner.

East: No stones here.

North:
Stone 16: In the northwest corner.
Stone 17 and 18: In front of the ramp to Stage 3 and on top of it.
Stone 19: In the northeast corner.

West:
Stone 9: On a big block.
Stone 10 and 11: Inside the big door.
Stone 12: On the way to the North.


In the southwest corner between Stage 2 and 3 is a stone on top of a broken blue tower. (Stone 15)


Stage 3:

South:
Stone 29: On top of a pillar in the southwest corner.
Stone 30 and 31: Right before and right after the big door.
Stone 22 and 23: Inside the big door.
Stone 32: Between the towers in the southeast corner.

East:
Stone 33 and 34: In front of the ramp to Stage 4 and on top of it.

North:
Stone 20: Inside the big door.
Stone 21: In the chamber the "Dark Passage" leads to.

West:
Stone 24 and 25: In the northwest corner, one of them is on the blue tower.
Stone 26 and 27: On top of two blocks along the way.
Stone 28: On top another pillar in the southwest corner.


Stage 4:
7 Stones are found here (Stone 35 to 41), four of them in the four corners (on blue towers) and three of them right in the middle of the North, West and South.

Stage 5:
Stone 42 is here, you can't miss it.


I hope this guide helped you, if i missed anything or got something wrong just write in the comment section below.