"No Weather, Bright (Lighting), Standard Terrain, Beach Biome, Ocean Biome, Plains Biome, Medium Biome Controller (aka Medium Biomes), Clear Modifiers, Zero-Length, Setting, Normal Sun, Zero-Length, Rising, Normal Moon, Normal Stars, Clear Modifiers."
It's probably worthwhile to add features like Crystals, Glowstone Crystals, Lakes, Lava Lakes, and/or Dungeons/Mineshafts/Caves if you want to do any serious resource-gathering of those materials, in which case they could go before the last Clear Modifiers. For a place intended solely as a base, those aren't as important. You can go with any Lighting level, as that doesn't affect monster spawning -- the Zero-Length Sun is in control of that, and Setting is pretty without allow mobs to normally spawn above-ground. You can also switch Plains for something else, if you prefer a more deserty or forestry tropical paradise, but I do recommend something that has at least a few dirt blocks.
The following Symbols /will/ always add instability : Dense Ores, Accelerated, and some variations of Tendrils (default and most types of wood will not, but so far every ore modifier combined with Tendrils did). Dense Ores provide so much instability that it's impossible to mitigate, but Ore Tendrils look like they can exist on a semi-stable world through the use of directed instability (specifically, 1xCharged, 1xScorched worked). Don't know about Accelerated.
In 10.3 and earlier, Biomes could go anywhere in the page order, but as of 10.4 they /must/ go directly before the Biome Controller to work, so it's best to start getting good habits now. Weather, Lighting, Terrain Type, Sun, Moon, Biomes-Biome Controller, and Stars are all independent aspects and can go in any order, but modifiers like length and such can do bizarre things if not place directly before the aspect they modify. In 10.0, there was a bug where Ages written without a Clear Modifiers phrase in certain places would always be unstable, so in more recent versions you can probably remove both of them in the above example.