You can't spot reduce. The only way to get "slimmer" sides (your obliques) is to reduce your overall body fat. You can tone the muscles of your sides but that can, in some cases, just make them appear bigger as you're building muscle underneath the fat. I have a friend who stopped doing ab work because she thought her stomach looked worse, not better.
If you're looking for some exercises to tone obliques bicycles are great. So is the side plank. I'm sure if you google those exercises you can find some visuals and a description of how to perform them. Also, if you start toning them now once you get down to your goal weight they should look less "flabby" and you'll probably like the look of them a lot better.
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