What type of garden, vegetable or flower? Where are you looking to put the garden? What zone do you live in?

flowering garden we are in Zone 7B. Thinking about border garden around the patio.

Lovely space for a border around patio. You need to think about how to water the area, what type of soil you have, how much sun will be on the area during the day. Pick an evergreen shrub you like and get 4 or five to plant around the semi-circle, not necessarily evenly. Get lots of bulbs that you can plant in clumps, mix in herbs and smaller perennials - leave space for colorful annuals. To begin with leave plenty of space between the plantings. See how they do and make changes next year to what wasn't totally successful. Voila!

You poured a big cement slab around an existing deck? I am deducting engaging points for that.

The first thing you need to do is sit down with pen and paper and draw the human traffic flow through this space. How does it work with the door, gates, stairs, maintenance needs? I for one do not want to have to come down from the deck on one side and walk around the whole thing to get to the patio on the other side.

Once you have the traffic flow figured out, you will know where the planting beds can go.

This view of our lawn ( courtesy of Google Earth) shows planting beds adjacent to the patio and perimeter of the lot. This was professionally planned Highly recomnended because selecting plants for soil type and placement/spacing is critical.

More than anything else, I would want small trees for shade around that baking hot area. It will be essentially unusable without shade. Place the trees mostly to the west/southwest first and east/southeast second. Shade cloth alternatives do not begin to compare with the shade cast by trees. Then plant a shade garden under the trees.

Good to hear Vinod. Good traffic flow is still the place to start in garden making. Pets and humans always prefer the shortest route.