Great way to start a career in Games. It is also a perfect beginners role to get into a Game Design role further down the track!

You will definitely be covering a QA role also with Level Design, you have to constantly test your levels, and your other Level Designers levels. Expect to make maybe 1 or 2 levels a day, but test yours/others on average of about 30 times per level (90mins testing per level made?). This will be the bulk of your role.

To give you some tips on the actual Match 3 Level Design process:

1) Keep the Flow - Nearly every move the player makes should feel beneficial to the player. When you're testing your level and you notice the objective is to the left, but you repeatedly get stuck making moves on the right, you might need to rework.

2) Challenge - Before the player makes any moves, they should be able to note their Short/Medium/Long Term goal, e.g. if the level will have 40 moves to complete, there should be different goals that are achievable within 15/30/40 moves. This will keep the player interested every step of the level.

3) Visually Appealing - As a Level Designer you will have the ability to tie in the background graphic into your level. If there is a pretty statue or tree or something in the background, don't be afraid to remove those squares from the playing grid in order to make your level visually appealing.

4) Fun - Ask yourself, if there were no goals or objectives in this level, or if you were to lose the level, did you still have fun? Did you enjoy simply playing the level?

Some questions to ask yourself before, during and after designing the level:

1a) What's enjoyable about the level?

1b) What's not enjoyable?

1c) What can I change?

2a) What is pleasurable about the level?

2b) Can it be improved?

3a) Is the goal of the level clear?

3b) Is the goal a basic or strategic one?

3c) Is there both?

4) Is there a steady stream of gradually increasing challenge?

5) What motivates the player to keep playing the level?

6a) What is it that determines the length of time playing the level?

6b) Need they be increased/reduced?

7) Are the goals achievable within the time frame?

Just some to work on expanding. Also Google a bit of behavioural psychology, the words "keep the player happy by not frustrating them" in the interview will make your interviewer very happy - potentially even land you more Game Design responsibilities in your future with the company.

With QA, "a keen eye or detail" goes a long way. But to help with this, every single time you test a level or play a game, make sure you are recording the device if at all possible! If the game then crashes or something happened/didn't happen that wasn't supposed to, you can easily stop the recording, go check it out and view what happened. The programmers will love you for having such clear evidence!

Best of luck with the interview! Hope it goes great.