How to show a series of images in a video using Final Cut Pro?

I was making a video, which has 12 photos / images, let's say, each one is displayed for about 30 seconds in the video. I noticed in Final Cut Pro, I can arrange the images "side by side", but then the final video may have 0.2s of black gaps in between, which can be annoying to the viewers. If I drag the edge of the image to "shown longer", it may bump the image next to it to a "higher level" (a higher level timeline), and it appears the "higher level" image would cover up the lower level image (the display precedence). However, what I did later on was a staircase of images... like a stair of 12 steps... which is messy, because when viewing the top most image in the project, and I cannot see how it relates to the sound timeline. What I did later on, by trial and error, was: I make image 1 and 3 wider at the edge where they overlap with image 2, and image 2 is bumped up to a higher level. Now I do the same later on, so that image 4, 6, 8, etc, are also bumped up to level 2... so it is just like a zigzag pattern with only 2 levels. Image 2 will take "precedence" over image 1 and 3, and so there is no tiny gaps whatsoever. Image 4 takes precedence over image 3 and 5, and so on. But is this the proper way? Is there a way just to place them on the same level and use some tools to "make them all go into a perfect series with no gaps"? Or better yet, make them go into a perfect series and also have a 0.3s or 0.5s or fade out fade in effect? Right now if I have to do transition animation manually by hand for all 12 images, I'd go crazy. (it is opacity transitioning and it is not easy and each one can take 30 seconds if I am fast, but 12 of them means it'd take 6 minutes). Maybe if Final Cut Pro doesn't have such a feature, maybe iMovie has it? (I was trying Windows Movie Maker some 10 years ago and it did have a function just to automatically let me add 10 photos and add fade out fade in for them all automatically so it took me 5 seconds to do it).