Once you obtain a level 13 Finca, you can create and save Base Layouts!
You can save both building and Sicario placements into a Layout. To do this, simply click on your Builder's Cabin and select the arrow cross button. From here you can save your Layouts in various save slots. Switch between your Layouts to find an optimal defense strategy.
Objects built after saving your Base Layout can be placed in areas that are free.
Be sure to save your current Base Layout before switching to another, or it will be lost!