What type siding do you have?
Got a real picture of where you plan on building this?
Unless you build this as a free standing shed and side all for sides and just set it close to the house there is only one right way to do this.

 

it will be on the other side of the house where there is no lines. but same slope, size, siding. I will obviously make a foundation for it.

I will side 3 sides, but as security purpose, I will side the 4th side from the inside and try to make it water tight from inside and outside (side facing the house)

If so, what is the best way to do this? Ive already built a shed, came out great. wate rproof, snow proof with 90+ mph winds. but now attaching one to my house is a different story lol

 

That's just a really bad area to try to do this!
Where's the water going to go coming down that hill?
That whole area would have to be excavated a footing poured, a reinforced block wall built at least 12" above grade, drain tiles, and waterproofed on the outside for this to even remotely work.

 

https://imgur.com/a/64Dqn1n

 

You need flashing behind the siding and you should want it behind the house wrap too.

 

shoot yeah I figured that would be the case. I could cut the siding and just add it as a house attachment. Was just wondering if there was another easy way.

or perhaps just add it as an accessory and get it as "close" as possible to the house.

appreciate the feedback. Any other ideas, feel free to post!