this is what I did to get my cover for Silver Trickster (aka the book I haven't updated in 20 years) and it's kinda simple, kinda hard, just depends. I recommend to edit the photos you want to use before doing this, along with making sure the colors look nice together, but other than that lets get started!
Superimpose
i. okay so first off, to get the circle image, i went to Pics Art and used the shape mask to get it. You can either make it to where you already put the image in the circle (first image), or you can make the black circle as pictured below. Or, if you're lazy like me, you can just copy that image below this one to make things a lot quicker/simpler.
ii. Open the circle image in Superimpose as the background and your first image of choice as the foreground. Go to transform and select screen so that it's in the circle image. Move it around as desired and merge and save the image. Repeat for as many circles as you want for your cover.
iii. Open a white background that is 2:3 crop size and add all of your circle images. You'll have to add them one at a time and merge every time you get it where you want it. To get rid of the white border around some of them so they'll overlap right, either use the magic brush or you can try the darken tab under mask and see if that looks right to you. Do this until it's positioned as desired.
iv. If you want a colored background on it, (I advise to use a lighter color to make this a whole lot easier) you first open the color of choice as the foreground and make it fit the cover. Put it on darken and then use the brush to erase unwanted color parts that overlap the circles. If some of your circles have white on them, don't forget to brush away the circle part of that too to make it look right.
v. After you are done with the coloring/positioning, you save the image and open it in Phonto to add your title and such. I used CODE Bold font, in case you wanted to know.
Pics Art
i. Look at the first step for Superimpose. If you choose to copy the image above and use that as a template, all you have to do to get your image in it is to add your image in Pics Art, set it on screen, and then move it as desired.
ii. Get a plain white background that's the right crop size (for Pics Art, it's 200x300) and then open all of your circle images you made in the step before this. Move them around as desired for your cover. Make sure to set them on ether multiply or darken to get rid of the white border part.
iii. If some of your circles overlap like the second image above, just use the brush tool to brush it away. Make sure to turn your hardness of the brush all of the way up as well; you want crisp, clean edges!
iv. To get a colored background on this one, just look up above at step iv. for Superimpose. All you do is add the colored image, put it on darken, and then brush away unwanted areas. Save and then add your title.
If you're wondering how I edited some of those circles, I can post a tutorial on that as well. It's quite simple; just a lot of experimentation. Comment which ones you really want to know how I did and I'd be glad to add that in there.
Just wanted to add that this was inspired by lydiasmrtin's edit on instagram, which is 50x better than mine no lie. I recommend to check her out if you ever need some inspiration (: