the product that is inside the container.
the rectangular shape of the carton is convenient to me because it has corners, it a rectangle, and the width is not so wide that it'd easily fall off of a window sill. rectangular shaped containers are better than rounded shapes because several of them can be placed up against each other to share light and warmth.
using a carton - cut one side of the container so that it can be turned up. write the name of the seeds that you planted on the flap. see the image above.
drainage is another feature to provide in your make-shift planter. store bought seed starter trays come 