Here is my Sanctuary build, I tried not to go to crazy large in this build, mostly utilizing the existing buildings and also keeping the junk low as well. This build has no unwanted or needed mods to download and since it's purely vanilla you can use your own mods and make the changes as you please or just leave it and enjoy it as it is. 

It comes with all level 3 vendor stalls and all crafting benches. Since Sanctuary is far north I added the Bunker Hill trading post to the blueprint, I also slipped chairs into the metal toilets so that settlers at times will sit on the toilets. 

This settlement comes with a siren gate closing system but unfortunately Transfer Settlement Blueprint doesn't know how to wire snap on the logic gates thus once the transfer is complete the gates will be closed and non functional so to fix this, the logic gates will have to be unsnapped and stored in the workshop and then replaced back to their original position and then rewired, so once after you've ported away and returned then make the changes. Please take note on how to wire them back by viewing the pictures and or viewing the video below, if you try to re-snap without first storing in the workshop it will cause a  CTD. If it becomes a problem you can just omit the logic gates by leaving them in the workshop and replacing the electric gates with manual closing gates. If any questions please ask. 

Logic gates used 

• NAND Gate
  

Logic gate wiring instructions

• Connect Power to Siren
• Connect Siren to “NAND Logic Gate” positive side 
• Connect Power to “NAND Logic Gate” positive side
• Connect negative side of “NAND Logic Gate” to Master Switch
  

Scrap and store
I don't use scrap everything so be mindful of what our scrap if you use SE
Scrap everything, if you decide to keep the crafting stations move them from their current location into the street getting them out of the way and place them where you want later. 

This settlement comes equipped with

• 31 beds
• 186 Defense
• 100 Power
• 49 Water
• 3622 item download
  

Importing the blueprint 

• Enable ‘Import original items (not built by the Player)
• Enable 'Import DLC items 
• Enable Nuke marker based items'. (I choose this option as I feel it gives a safe and successful Import and Export).
• Enable 'Import wired power connections
• Enable 'Restore snapped power connections
• Please be sure to read thoroughly the import  Success instructions on the Transfer Settlement Blueprint  site located in descriptions and the post section as a sticky.
  

My other Settlement Blueprints

Finch Farm
County Crossing
Abernathy Farm
The Castle
Starlight Drive-in Remodeled 
Oberland Station
Taffington Boathouse
Outpost Zimonja
Hangman's Ally
Nordhagen Beach
Somerville Place
Starlight Drive-in
Greentop Vanilla Blueprint
Sun Shine Tidings 
Red Rocket

Credit goes to CDante for making this possible

I'd like to point out another fantastic builder  FiddleFlap checkout his builds