The frame within a frame and Dutch angle are both compositional elements that can enhance the composition of your photography.  The frame within a frame technique can be used to add an extra emphasis on the subject of the photo. The Dutch angle is angling your photo around a 45-degree angle.  This adds a unique perspective and a more unusual composition. Although, if your angle is too small, it could appear as if it is a mistake. In order to avoid this, make sure your angling is always purposeful and intentional.

The image above is an example of a frame within a frame. The tree branches frame the subject, the rock in the ocean.  

This is another example of a frame within a frame, as the stone wall frames the subject, the house.  This also shows that you do not need to frame the subject on all four sides.  

This photo is an example of a Dutch angle.  The angle is clear and intentional. The reason it has been used here is to accentuate the feeling of the landscape, adding more emphasis on the lines of the fields.

This is another example of a Dutch angle.  In this case, the angle was used to emphasize the tone of the photography, along with emphasizing the horizon line matching the line in the subject’s sweater.  This adds to the overall dramatic effect of the scene.

Frame within a frame and Dutch angles are just two examples of many different compositional elements that help to make your photography better.  This being said, both of these techniques should be used sparingly and in the right circumstances to accent your work. The overuse of them can end up making your work look tacky, causing more harm than good.

Sources:

https://expertphotography.com/frame-within-a-frame-depth-contex/

https://en.wikipedia.org/wiki/Dutch_angle

https://www.studiobinder.com/blog/dutch-angle-shot-camera-movement/