Measure the circumference of the child's head. Cut a piece of cardboard to a length that is double the circumference measurement obtained. Cut the piece to a height of 6 inches. Wrap felt around the front of the cardboard strip and secure in the back using multipurpose glue. Cover as much of the cardboard as possible and trim the felt as need be to get a tight fit. Allow the glue to dry.
Cut a piece of cardboard in to a 12-inch-by-12-inch square. Cover the square with felt and glue on the underside using multipurpose glue. Cover all areas and use extra pieces of felt to cover all portions of the cardboard. Allow the glue to dry thoroughly.
Bend the felt-covered cardboard strip to form a circle. Staple closed to form the piece that rests on the child's head. Adjust the circumference as necessary by checking the fit by placing the circle on the child's head.
Lay the felt covered square upside down on a table. Place glue on the entire circumference of the circle strip and press the circle to the flat square. Hold in place for one to five minutes to get a good seal started. Allow the hat to dry.
Glue colored yarn on the top of the hat to create a tassel.