Having looked at several news articles from UK today, I now realize that. Well done, I must say!
Actually, this is one of the simplest techniques using GIMP, the free alternative to Photoshop.
There are dozens of instructional videos on YouTube that show you how to cut out a person from a background.
Download GIMP and install it on your PC. Then check out this video (as an example).
When I do these memes, I spend most of my time figuring out the composition of the image.
The idea is to let the pictures you find guide you to the best composition. You are very unlikely to use your original idea. Let the associative power of the Google Image collection steer you to something you like.
I spent 30 minutes on Goggle trying to find the right background. I always search for Large sized photos and you can specify that search in Google Images.
Liz commented the dress looked Grecian. I thought so too, so my thought process went through stages until I found a picture I found suitable:
This process is a lot of fun. And once you get hooked, you'll want to do more.
Best of all, FR is an appreciative audience for displaying your images!
Finally, last year I made an instructional video of my own on the process of creating memes. The video is on YouTube and the title is Making Deplorable Art.