Materials needed:

a. oaktag, construction paper, or other stiff paper cut 20 inches square
b. pencil, pen
c. ruler
d. scissors
e. glue
f. cardboard 
g. sand (optional) 

1.. On the paper, already have 7 1/2 inch square drawn 

2.. Divide each side of the square in half and draw lines (as shown in figure) that extend 6 inches from the midpoints on the sides as shown. Mark these points A, B, C. and D. 

3. Draw lines from each point to the corners of the square closest to it (dotted lines, figure 2). This will make four triangles with sides of equal lengths. 

4. Draw  fastening two tabs on the triangles that are opposite each other as shown in Figure 2. Each tab should be about 1 inch wide and 2 inches long. Draw the tabs roughly on the middle of each side. 

5. Draw diagonal lines connecting the opposite corners of the base square; label each triangle 1,2,3,4. 

6. Fold side up, using glue on tabs 1 and 3 to attach to 2 and 4.

7. To make base, cut 12 inch square of card- board and spread with glue and sprinkle with sand.

Glue bottom of pyramid to base. 

Go here for a unit study on Egypt:
Let's Study Ancient Egypt Part I
Let's Study Ancient Egypt Part II
Let's Study Ancient Egypt Part III
Let's Study Ancient Egypt Part IV
Build an Egyptian Pyramid