Start collecting your used milk and juice carton. Do remember to rinse the inside with water and drain before storing them. If you don’t you will find green and black aliens inside it as you cut through it.

Outline the shape you want to cut out for the opening with a ball pen. I know you love gel pens but that won’t work with this craft. The outer part of the carton is glossy and water resistant so ball pen works the best. Use a craft knife to cut through the carton following the outline you made. Do the same for the other side. 

When you have made all the openings or holes on the carton, you are ready to prime them if you want. Place a drop cloth to protect your table. You can use a water based primer or even chalk paint.

Then you can also paint it together. 

Cut through the carton to make a hole for the stick using a craft knife. Slice an X mark on the spot you want to insert the stick through. Then just poke through the X mark all the way through until the chopstick goes in. 

Then make a hole on the top of the carton where the string will go through. Use the craft knife and again slice through making an X mark at the center. Then poke the hole so it will open wider. You can now pass the string through and make a knot. Your bird feeders are good to go from here.

References:

DIY- How To Turn A Milk And Juice Carton To A Bird Feeder