I assume you are aware that the conifers you are looking at will completely hide the house from the vantage point of the picture. And I'm not sure why you feel you must use only narrow conifers.

I wasn’t planning on placing them in the middle, just 3 on either side but I am open to suggestions.

If you were planning to have a skinny conifer as a foundation planting, you need a picture that shows that. From this distance, I don't see any place for skinny conifers to complement the architecture of your house. From this angle, I'd put your weeping spruce half way up the hill on the right corner of the yard (as shown).

It's a lovely house, you really need a plan to address the whole of your landscaping, rather than buying trees and wondering where to put them.

I've done this with smaller plants. I learned my lesson, particularly after discovering shorter plants ended up behind taller plants. I now focus on the bigger pieces, like shrubs in areas where I need more shrubs. And smaller pieces where I have enough shrubs. My lot has too many, too big trees, so I don't buy any, no matter how much I drool over them.

You can do that, too. For example, if I were you, I might put some shrubs on that slope between the saplings and the sidewalk. You might specify 5 shrubs, no more than this tall and liking the sun/shade and your soil. You might pick a color range -- whites, yellow/orange/peachy pink, purples/pinks/blues, etc. Then, you can go to the nursery or on-line and be inspired confident that if it meets your requirements, you know where it will go, more or less.

What are the three decidous trees planted on the slope?

These are dogwoods. They have been there for 3 years and yet to bloom. Will see how they look this spring.

Not a pro but to me, the Dogwoods are the focal point. I would place the new tree on the left to blend in with the other evergreens.

Then concentrate on low shrubs and groundcover for the remaining bare areas. For the sunny areas, I know deer don't like Lavender and Salvias attract hummingbirds and then a few cascading plants like creeping Rosemary for over the brick wall. Native grasses always add nice movement in the breeze.

For the shade I would research flowering groundcovers. Your local nursery is a good option.

You may get deer on the sidewalk or top lawn, but they are less likely to stand on that slope, so the middle of the slope is the place to put plants tastiest to deer, if you have a major deer problem. Deer are less likely to stand on the sidewalk, next to the road, so unless you have a major, major deer problem, I'd think most of the slope is fairly safe. Obviously, tailor it to the degree to which deer are a problem. If they are a huge problem, stick to plants with at least some deer resistance, but you won't need the most resistant. If they aren't much of a problem, you might be able to get away with deer candy on the slope. The flat part of the lawn , particularly bordering your trees is another story.

You’re always spot on, Sigrid! Interestingly enough, deer came browsing yesterday and I scared them away. They came up the driveway and accessed the Gold drift weeping spruce from the flat front yard. I am in the process of working with a designer for the full scale. I placed it where you had suggested, and will probably get a some boulder around it hoping that will hinder access. It’s wild how persistent deer is!