For this Design I used assets from Freepik: Hand gezeichnete dekorative mit Blumenelemente | Kostenlose Vektor (freepik.com) 
Please know that you can't use them for selling products as main focus of design. So this Wall Art is only for personal use.

For the end result it's made within Adobe Illustrator and usage of Shaper Tool. This way you create all parts seperatly and then selecting all and create the shapes you want. This way I also created the Score lines for easier placement in assembly

Green = Engrave

Violet = Score (Help for alignment in assembly)

Red = Cut

1.  Color if wanted
2. Add glue to pieces and glue to background layer

No big deal, just glueing pieces.

This is the final piece and I think ist very cute and a fun door hanger. 

For mine there is a mistake but thats fixed inside the XCS file. 
Have fun creating it! ~Anzy