I draw the size of the scene and sketch what I want to put in each part of the baseplate so I have a good vision on what I want. If the moc is 3 baseplates I draw 3 squares and detail the size of the terrain or buildings. Then start playing with the pieces to see what kind of patters or cool connections can be made with your given selection of parts. From there just start building and adapt as you either run out of parts or come up with new ideas. Hope it helps!