One of the goodies you get in the City Sidewalks collection is a set of skinny washi tape. We also used the "Very Merry" stamp set that has this great saying in bold letters, "Very Merry". By tearing washi tape in progressively bigger sizes, and stamping the "Very Merry" in Willow, the tree shape forms. Add Kraft cardstock for the tree trunk.
The second technique is the way the card is put together. It's called Joy Fold card and instructions to build one can be found here at splitcoaststampers. It's a double fold out card, and is a fun surprise when opening it.