I would appreciate posting of methods of how to get scenery (such as double boxes) lined up perfectly without waisting a lot of time. Thanks ;-)
The Ghost Merging Guide has most of what you'll need in it. That'll teach you to merge, but it can be hard to get things lined up without practice. Pay particular attention to pre-bracing and using a 2nd controller to line things up correctly. Another thing I'll mention that should help you is to notice that when you spawn an object, it is always oriented at perfect 90 degree angles with the grid. Spawn something like a block, large and set it down gently without rotating it at all on a flat surface, and you've got an unmovable and perfectly straight object to measure angles and pre-brace against. For example, a wedge, large set sideways against it measures you a neat 45 degrees. Also, in the future questions like this one go in the Forge Discussion forum. This "Gaming Discussion" is for non-Halo games.