Just xor bit by bit against real random noise,embed it in a massive stream of other pure random, remember the offset, if it's really that important..
It is also provably secure unlike every other cryptosystem.
That's what google did with CECPQ1, they use "new hope" which is a quantum resistant algorithm with traditional methods (X25519). That way if new hope is cracked, they are still using an industry standard you'd have to crack as well.
if you are not doing that, best stick with known good encryption schemes.
that being said you can implement a lot of encoding schemes like you say in ways that make it arbirarily hard for people to decide what is junk and what is data, to make it nearly impossible to crack especially if you say do that xor with random values etc. because if you'd receive a data intercept you have a hard time to rebuild the data from the junk and then decode it