OK, so, hear me out and picture this in your head:
It's the summer of 1965. You're sitting in your hot, stuffy office. The place doesn't look all that great, but you along with a team of skilled vexillologists have been assigned these offices for a very important, aesthetically-geared task; designing the flag for a nation of seven and a half million people. This nation will be composed of two former colonial bodies, Negresia and Gruenia, with a representative democratic government being located in the old capital of the latter.
Negresia is a densely-populated subtropical archipelago playing host to 2.5 million people. It bears a resemblance to the Solomon Islands, with a native Melanesian people comprising 84% of the population. The other 16% of the population is mostly white, coming from a Scando-Germanic nation known as Sunthreit. Negresia is poor in resources, but manages to sustain its economy by exporting rubber, fish and various tropical cash crops (making it dangerously close to being a banana republic). The nation's name stems from the Latin "Nigrum", or black, a reference to the colour of its native inhabitants (like IRL Melanesia).
Gruenia is a temperate pair of long islands, larger in both population and land area than Negresia. Gruenia boasts a population of 5 million people, almost all of whom are whites hailing from Sunthreit. In the northernmost parts of the country exist a native people similar to the Negritos of South Asia and Malaya, but they are a very small minority who have suffered population-wise at the hands of disease, massacres and relocation from their traditional coastal living grounds. Gruenia's native animals are a near carbon copy of New Zealand's, except due to a less intensive native occupation less animals have gone fully extinct. Gruenia has abundant resources of coal, silver, iron ore, limestone and gold that have allowed it to become an industrialised country, with better living standards than Negresia. Gruenia is named after Jerwald Gruen, a Sunthreiter explorer and cartographer who lead the first comprehensive expedition to the islands in 1693.
In this flag, it is recommended you represent both countries. Patriotic sentiment exists in both of them, with the federation of Negresia and Gruenia into one country being a choice directed by the civil war-stricken motherland. The national colours of Negresia are ocean blue, canary yellow and forest green, and the national colours of Gruenia are black, white and forest green. Symbols and features recommended and suggested for the flag are:
-a Southern Cross of some sorts, preferrably with five-pointed stars
-a Mannaz Rune, the symbol of Sunthreit (the mother country). This symbol is the only one that's pretty much obligatory. It could potentially be put in a black canton.
-the integration of a wave-looking pattern or pacific islander patterns into the flag
-the integration of North European folk patterns into the flag
-a way of integrating both countries' national colours without it being two tricolours on top of eachother.
-a Moa bird is the designated national animal of the new federation. The national animal of Gruenia is the Haast's eagle, and the national animal of Negresia is the sea turtle. It isn't recommended you use all three at once.
-two stars representing the two nations
-a coat of arms depicting the any of the above features and the national motto (to lead is to serve), held by a Melanesian native and a European. Bonus points if the Melanesian is holding a spear.
Of course, with so many suggested features, it's natural to just go and discard a few. Do it. I know you want to.
Oh, and good luck, brave vexillologist.

