First, have students draw a Christmas tree using triangles. They can use three or four triangles to do this. I have found that it is better if they use a ruler to create the triangles. It helps them get the shape more exact which makes it easier for them to measure it.
Next, have them draw the trunk of the tree and three or four presents in the shape of rectangles.
Next, have the students use their ruler to draw parallel lines and perpendicular lines on the tree and presents. They can erase to make the lines appear to cross like ribbon if they want or they can just leave the lines actually on the paper.
Let them add other decorations to the tree and presents. They can do this however they wish.
Finally, have them trace their lines with a black permanent marker and add color. They can use water colors, tempera, crayons, colored pencils, or pretty much anything else.
Here are some from students:
This is a great lesson by itself, but if you really want to hit those math skills you need to check out this TpT resource that I created to accompany the lesson. Students measure and find area/perimeter. They also write about and analyze the measurements. Then, they reflect on their artwork. It is available for purchase for only $2.00. I hope you like it!