FOSS gamedev and creative worlds

So this may just be a problem on my PC, but it is quite annoying. I wanted to load a world that was flat with no trees, caves, or dungeons. As most of us know, this can be done by going into the map_meta.txt and getting rid of those parts and changing noflat to flat. Well I tried this, and while SOMETIMES my world loads flat, it will still generate with trees, caves, etc... I have generated a world like this in previous versions (and it worked fine). Also note that when I look back at the map_meta.txt, the mg_flags had reset themselves (which obviously tells me something is wrong). I have tried changing the settings at different times (as it is ideal to do it before you first load the world as to not generate anything) and in different ways but it never works. I had the thought that the problem could be the More trees mod but i disabled ALL the mods and it still generated trees (although even if that were what was making the trees, it doesn't explain why the caves and dungeons still generate). Yes, I have looked at the wiki and anything i can find (and I even emailed Mr. Ahola/celeron55...probably should of started the forums sooner...). All he gave was the link to the mg_flags part of the wiki (which is no help at all). If I could have some help that would be great! :)

By the way, this is my FIRST POST!

most flags are mapgen specific and only work with certain mapgens.
to prevent dungeons from appearing on the surface, you should uses "no_floating_dungeons" (probably, not sure if i spelled it right).
trees are generated differently on mapgen v6 and v5/7.

if it worked in previous versions, i guess you have to use v6. it is still the same a s always and supports most flags.

v5 and v7 have been changed a lot to support custom biome definitions.
you could also make a mod for mapgen7 that creates an empty world.

will overwrite the default biomes and decorations with whatever you register.
if you don't register anything, you will get a stone world. (like in previous versions)

You could try to set these options in your minetest.conf file instead of the map_meta.txt file. But then they will apply to any new world you generate. I have it set up like this in minetest.conf currently:

You should also change trees to notrees to disable trees. With this I'm getting completely flat worlds without dungeons or caves, but also no water.

You should set flags in minetest.conf before starting a new world.

Thank you ALL! I used Dartmouth and paramat's way of doing it. It worked like a charm! :D