21 - 7 interlaced dots (Idukku Pulli) Kolam.
Start with 21 dots in the center and stop at7 by putting interlaced dots at both sides as shown above.
Join dots and put extra dots in the four corners as shown above.
Erase the extra dots around the Kolam.
Join the four dots inside the box as shown above, or erase the four dots as shown below.
Draw thick lines and fill with desired colour powders. To highlight the dots, I have given more space between the dots. If you put the dots little close, you will get perfect size.