If "tricky" means difficult or challenging:
* Easy
* Simple
* Straightforward
* Clear
* Uncomplicated
If "tricky" means deceptive or misleading:
* Honest
* Straightforward
* Genuine
* Transparent
* Open
If "tricky" means clever or cunning:
* Naive
* Straightforward
* Unsophisticated
* Uncunning
* Simple-minded
The best opposite for "tricky" will depend on the specific meaning you want to convey.