It would be helpful to know more about where you live. Southern Ontario has many different zones. Even Toronto has 3 zones - and they are very different, having gardened in the warm one near the lake and a colder one nearer the 401. https://www.plantmaps.com/interactive-ontario-plant-zone-hardiness-map.php
I'm another one who wouldn't remove those evergreens.
I also have a slope at the back of my property. I've planted quite a bit of it with evergreens and evergreen ground cover to avoid having to pull weeds or maintain perennials on that slope. Planting on a slope means the water runs right off, so you need drought tolerant plants. With an east facing bed, especially with a solid fence to the south and the shed also shading some of it, you have both low water and relatively low light. You need some tough plants to get established there.
I have used a lot of vinca as ground cover which, when established, is totally maintenance free. Blooms now with blue flowers, evergreen. A tip for planting it in a tough spot, just lay it down and plant the whole stem underground with just the top leaf or two sticking out. It looks weird but if you plant just the roots, most of the leaves will die anyway and sometimes the whole plant, and it will take forever to get established. If you plant the whole thing then it will root wherever a leaf attaches to the stem, and it will look great in no time.
For lowest maintenance, plant the back 8 feet with evergreens and leave 2 feet at the front for annuals.
To give you an idea of how many plants and shrubs you'll need, these are 4 foot shrubs with annuals at the front.
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planting on an east facing slope/border planting vinca on a slope plany layout
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