Draw a grid of 25 equally sized square blocks on a piece of paper with a black marker. Draw the blocks in five equal columns, containing five blocks each. Use a ruler to help you size the blocks the same and to aid in keeping the drawn lines straight.
Color the first five-column row of blocks with a bright yellow highlighter.
Color the bottom row of five blocks with a brightly colored blue highlighter. The first block shared by each color will turn green.
Color the remaining blocks with the two pens ---- first yellow, and then blue to make the same green color as the shared block.
Explain the math behind a squared number, emphasizing that five squared means 5x5=25. Show the picture representing the first column of five yellow blocks to represent the original base number. Next, point out the four additional rows of blocks. This shows that in squaring the base you're multiplying the base number by itself, thus five groups of five blocks. Finish the explanation by pointing out the total set of 25 blocks representing the sum of the multiplication.