The Build Faster mod gives you several new tools for crafting structures in bulk. You can place multiple blocks in a line up to 64 blocks and even copy and paste existing structures with just a few clicks.
With the Claw of Boundary Creation you can select a cube or section of space by clicking one end/corner and then clicking the other end/corner. Then right click to take selection anywhere else you want and hold left click to place it.
There are two wands capable of laying down a row of blocks: The Destructive Linear Conjuration wand and the Non-Desctructive Linear Conjuration wand. One will replace the blocks lying within the frames and the other will stop placing once the frame hits an already placed block. You can shift + scroll to change the number of blocks you want to place up to 64. You’ll also need to put the block you want to place right next to the wand in your inventory row before placing.
You can even place blocks in mid-air!
But most importantly you can quickly undo the previous few changes by right clicking with any of the wands.
Important: Unfortunately this mod is no longer available!