There are two ways to approach this. One is to mist your origami heart with water lightly and gently press it with heavy objects, like books. However, this method is tricky, as it may create wrinkles in your heart, and too much water may cause it to tear. Another method is to use adhesives. Personally, glue sticks have provided our project with great results. The drawback of this method, however, is that if excess glue is used, it may create grey markings around the edges of the heart. However, if done correctly, both methods provide satisfactory results.