One of the nice features of the Olympus EM1 iii is that it can automatically take and composite into a jpg, a series of images focused at slightly different distances, so you can get a greater depth of field than you would with just one image, and you can use a larger aperture to avoid diffraction from small apertures.

This was shot under a fluorescent desk lamp, with my camera on a tripod. I took advantage of the swiveling lcd to compose the image and tapped on its screen to capture the image(s).

Very easy. Robin Wong has a good tutorial video about how to use in camera focus stacking here: https://youtu.be/pc7y28vkb3Y