Step 1:
This is the front of the paper, turn the paper.

Step 6:
Valley-fold over these 2 lines.

Step 5:
Squash-fold the flap.

Step 2:
Prefold over these 4 lines.

Step 4:
Valley-fold this flap upwards.

Step 3:
First, valley-fold over the 2 lines at the bottom-right. Then mountain-fold over the 2 diagonal lines in the middle. And valley-fold over the 2 lines at the top-left.

Step 10:
Valley-fold the triangular flap upwards.

Step 8:
Pull the edge indicated by the purple arrow downwards by making a valley-fold over this line.

Step 9:
Push/press the edges indicated by the purple arrows downwards.

Step 7:
Unfold the folds of step 6

Step 16:
Valley-fold the edge indicated by the 2 upper arrows to the edge indicated by the 2 arrows below.

Step 15:
Pull the 2 ends at the bottom of the arrows outwards, in the direction of these arrows.

Step 12:
Mountain-fold the triangular flap to the inside of the model.

Step 11:
Pull the 2 ends at the bottom/back of the arrows outwards, in the direction of these arrows.

Step 14:
Repeat steps 5 to 13 on the other 3 flaps, see arrows

Step 13:
Push the 2 ends towards each other again, see purple arrows.

Step 21:
Fold the center downwards over these prefolded lines.

Step 19:
Prefold over this line. Fold the tip below to the height indicated by the upper arrow

Step 20:
Open the model, see arrow

Step 18:
Bookfold one layer to the left, do the same on the backside of the model

Step 17:
Repeat step 16 on the places indicated by the 3 purple arrows

Step 22:
Push the model inwards from aside again

Step 28:
Valley-fold over the line below and mountain-fold over the upper line.

Step 25:
Bookfold one layer to the right

Step 26:
Repeat steps 23 to 25 on the left (mirror-wise), see arrow

Step 24:
Valley-fold the end above the yellow line downwards

Step 23:
Bookfold one layer to the left

Step 29:
Mountain-fold over this short line.

Step 27:
Mountain-fold over the line below and valley-fold over the upper line.

Step 30:
Valley-fold over this line

Step 31:
Mountain-fold over the upper line and valley-fold over the line below.

Step 32:
Push the edge indicated by the purple arrow inwards by making an inside reverse fold over these 3 lines (=valley-fold over the line in the middle and mountain-fold over the two outer lines).

Step 33:
Mountain-fold over these 2 lines

Step 34:
And valley-fold over these 2 lines.