Hi @johndevine,
A warm welcome to the Bunnings Workshop community and thank you for your question.
How large an area are you looking to tile and how much variance in height are you looking at?
Some photos of the area will help our members understand the project and offer their best advice. Can I trouble you to upload some photos?
Let me know if you need a hand uploading images, I'm happy to help if required.
Unevenness can be managed by grinding down the high spots and filling in the low spots. As concrete grinding is not a simple task, if you need to grind back the concrete, I suggest contacting a company that specializes in concrete grinding for their assistance.
It is likely, that you will be able to simply build up the area with a screed that specifies it can be used outdoors. This Australian Builders 20kg Tile And Paver Screed is a good option if it is available where you live. Otherwise, look for a screed that specifically states it can be used outdoors or in alfresco areas.
The area is likely much larger, but the principles in How To Screed a Shower Tray apply.
Once you have created your slope, tiles can be laid directly over the screed.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
