First I cut out the shapes (heart, pine-tree, star): I used my cookie cutters for pattern. From the red fabric I cut out a little smaller shapes, from the white felt I cut out a little bigger ones. Then I measured the green squares: they should be a bit bigger then the heart/tree/star but not wider then your pillowcase!
Next I pinned down the shapes onto the green squares and sewed them, after that I pinned the squares onto the pillow case fabric (only front) and sewed them.
Finally I made the pillow case itself and also put a little label on the side and a button on the back. What do you think?