Here's a pretty solid workflow if you don't desire to use multiple objects in the creation.
I'm posting the image sequence for now, so I don't mess that part up, then coming back to give the commentary per image.
- Shift+A >> Mesh >> Plane.

- Tab to enter edit mode.

- I to inset the active face the desired amount.

- Delete >> Only Faces.

- Result of Deleting the face (giving you the major frame profile).

- A to select all faces.

- E to extrude the desired overall frame thickness.

- Ctrl+R >> 2 >> LeftMouseButton >> RightMouseButton

- Click on the Face Mode icon/button.

- Z >> Select the inner ring of faces (as shown).

- With your cursor just outside the outer edge of the frame E >> S >> Move your mouse toward the center of the frame the desired amount >> LeftMouseButton

- Click on the Edge Mode icon/button.

- Select the Edge Loops at both the Inner Top & Inner Bottom of the frame.

- Ctrl+B >> Move your mouse outward the desired amount >> Either type the number of segments & hit Enter OR scroll up on the scroll wheel of your mouse the desired amount & LeftMouseButton.

- Hit Tab & you are complete if you desire a 4-Sided frame.

- If your desire is to have a 3-Sided frame >> Tab to enter edit mode. >> C >> Select the bottom most horizontal edges of the frame.

- Delete >> Only Edges & Faces.

- The result is two empty holes that we must repair/fill.

- Loop Select the left most hole. >> F to fill.

- Loop Select the right most hole. >> F to fill.

- Select both Edge Loops again.

- S >> Y >> Numpad 0.
