ive never had problems with abs. ive been boxing since i remember myself.
i know a frined of mine that used to make 1000situps daily and he had none and i have em all. just start some cardio with low carb diet and you should be able to see em in matter of weeks.
dont do alot of situps, do 2-3sets max 15-25.
best way to burn fat is to do interval training,the kind that sprinters do.
warmup for 5 mins(running,bike whatever...)
then do 30 secs of your maximum..push to the limit and then 1 minute normal.
repeat 8-12 times like that and i promise that with adequate diet in few weeks ull have good abs. try getting some fat burners to that.