I've made a Space X Starship. The model is 36cm/14" high or can be scaled up as you wish. To assemble the ship just glue the segments together. The Starship consists of the nosecone and the lower ship section (6 engines). To build the booster you will need the 3 remaining parts (lower booster, upper booster, gridfin ring). Insert gridfin ring inte the upper booster part. The ring is a quite tight fit so you might need some force. After that glue the upper and the lower parts together.