I applied twice, so ultimately know the general format. You're asked to submit a cover letter and CV. Cover letter should be as creative as possible. They like it fun and unique. CV should be standard. You'll then be invited to the interview which is a group interview. You'll be put into little "teams" and asked to complete a task. One I was asked to do in both interviews was make a poster about the product "Charity Pot" (as it was quite a major product for my store). In your interview, you might be asked to "sell" them a product, but this one was slightly different. They simply just wanted information about the product to see what you could relay back to them in terms of product knowledge. So for example, ingredients in charity pot:
Cocoa butter - Moisturising
Vanilla - Nice scent & fairtrade.
Aloe Vera - Soothing and helps broken skin
Geranium - Nice scent and antiseptic value.
Etc. They just want to see what you know about things like ingredients and ethics and values. Don't waste time talking about benign things like portability, etc. Focus on the actual product and what it'll do for you.
At around Christmas, you may be asked about gift sets (which gift would be good for an expectant mother? etc.?) you'll be given a list of gifts to match, so don't worry about learning the entire gift range or anything like that, but focus on ingredients and the product contents.
For example, the gift "relax" would be good for an expectant mother. Lots of lavender to help promote sleep, lots of cocoa butter to moisturise the skin, etc. Just use your head!
Lastly they'll pull you aside one-to-one and ask questions. They change every time, but most of them are quite basic. If they're more personal, just try and be chatty and genuine. They'll like you more for it. Even if it doesn't seem relevant.
After this, you may be asked for a shop floor trial. The contents of this change dependant on the store. In my shop floor trial, I was asked to do at least three demos on customers. They'll show you round and make sure you can do demos on customers so you know how to first. The easiest demos are the lipcare demos of you want a bit of a cheat, and children tend to be the easiest to do this. If they're looking lipcare, ask them if they want to try something like the bubblegum lipscrub. It's tastes nice and sweet and is incredibly popular so they probably won't say no. Then you can lead on from there like "try a lipbalm on top to lock on moisture". Honey trap is a good follow-up. It tastes kind of like marshmallow.
However, they might ask you to do something else. It all depends on the store. They might tell you what's going on in advance, they might not. So good luck on that front! But other examples I know exist include:
Do x amount of skin care consultations (face masks!)
Sell x amount of gifts/sell a gift of x price
Help a customer with a basket that has a value of more than x.
Just try your best! If you're stuck, ASK HELP FROM OTHER STAFF. You're not expected to know every ingredient in a shower smoothie. They won't judge you or mark you down for it. It's better to get them the right product then wing it!
The, hopefully, you're hired! Good luck!