What is the easiest way to find Latias or Latios, as the case maby. ..

There is no easiest way to find Latias he just randomly appears in the grassy or water areas, not under water or in caves deserts or anything like that just grass or water.

I find it easy to just fly to Lilycove and go to the grass west of the city, if he doesn't appear keep flying back to Lilycove, trying again is how I caught mine.

You had the answer right there — you didn't beat the Elite Four.

OK, we have a few problems here.

If you have Sapphire, you can only get Latias, and if you have Ruby, you can only get Latios.

You can only find them after you have beaten the Elite 4. Once you have, they will appear randomly - there is no specific place where you can find it.

You didn't beat the elite 4!

Beat the elite 4 with a level 55 Kyroge.

You can find Latios by walking around and after you beat the elite 4 but you will need an eon ticket 4 Latias to visit southern island.

Pokemon SAPPHIRE: easiest way to find & catch latias

[read before trying]

1. You have to beat the elite four until it shows on the tv that a mysterious red flying Pokemon has been spotted.

2. You NEED to save your master ball. Is hard I know but possible. I caught all of the regis, rayquaza, and kyogre with only Ultra balls! It's hard but use it on latias mainly because you can save your game before trying to catch the others.

3. You need a Pokemon thats around...level 38-40. Make sure that pokemons in the first slot in your party. And it needs to know rock smash. So some Pokemon you never use that you got from Ever Grande Cities cave.

4. You're going to need a couple repels[I only used one but you may need more]

5. Fly to every city in the game except for Mauville. Then fly to Lavaridge. Go down the side to get to the to rocks that are blocking your path to Mauville. Use rock smash, and go into the gym.[ I'm not sure if this is necassary but I did]

6. Go down to the grass road instead of the cycling path and use a repel. Walk into the grass and walk around! You should run into her fairly quickly.

It literally only took 16 steps from the first plot of grass and ran into latias!
Just make you you have the masterball or else it could be hard catching her. Even if you don't have it youll now have her location and be able to track her down!

Hope this helped!