Import required materials, such as diamond pictures and background materials.

Create a new composition in AE, and drag and drop the materials to be used into the composition.

Set the diamond picture as a 3D layer, and adjust its position and rotation angle in the scene to achieve the desired effect.

Select the diamond layer and select Mask-New Shape Mask from the Add menu to create a shape mask layer.

Draw a diamond in the shape mask layer with the brush tool, and then set the shape path as the mask of the diamond layer.

Select the diamond layer and select Effect-Adjust Color-Color Correction from the Add menu to adjust the color and brightness to achieve the desired effect.

Add a "glow" effect to the diamond layer and adjust the brightness and size to create a flash effect.

Add a camera layer to the composition, and adjust the position and angle of view of the camera to get the desired effect.

Use the "Follow 3D Camera" option on the diamond layer so that the diamond layer always faces the camera.

Finally, adjust the animation timeline, render and export to the required format.

Note: The above steps are only the basic steps of making diamond flash special effects, and the specific production process needs to be adjusted and modified according to actual needs.