Does something like this works for you?
https://drive.google.com/file/d/15lq4Fz3rzJdIM7iXbC3JB79-IPjsTIzY/view?usp=sharing
I just imported the 2 stls in blender put them together, like in the same place as you wanted

Selected both as seen in the image, then File -> export -> STL. Make sure you have “selection only”.

Export it, open it in your favorite slicer, and that should work.
Blender can do a lot, I use it to design and modify a lot of things from thingiverse too, and I have learned a lot of tricks on blender too.
I also want to learn freecad to do stuff from scratch, but in the meantime blender does what I need.
EDIT: Most probably I did not understand the requirement correctly, is this supposed to have a hole? hit me up if you want, happy to help https://discord.com/users/poringo#6290
Another Edit: Oh something like this?




I have abandoned my ender 3, it is finicky and needs a lot of tuning all the time for sure.
What do you recommend I could get? Like in the same price range lol