I am following English premier League and Australia A league. 80-85% matches 1st half Happen corner over 3.5 that's odds 1.32-1.40 . So anyone wants to safe betting then you can bet there. Not all matches. Select for a team like Manchester United. If Manchester United and it's partner fail to cover 3.5 corner in 1st half in a match then the next match stake high between Manchester United Vs opponent team. That's the simple tricks. This tips dose not work for 100%, so bet your own risk.
It comes back to raw mathematics at the end of the day and the house is far ahead of the average sports better. Let's assume that the sportsbook adds a little edge to every bet, so in reality you see a 1.33 bet but at the core it is a 1.25 with a margin of protection for the house. That means that for you to win over the long term, you need to win once out of every 5 bets - at which point you've made 125% of your original stake in profit. However, if you were to lose just one of those games you'd be at 25% profit. This leaves very little margin for error and whereas you say it is not "100%" guaranteed, there are actually quite a few games out there with over 7 corners total (over both halves) which can easily translate into 3.5+ corners in the first half. Just remember, you're up against these sportsbooks with very deep statistical analysis going on, so it's almost impossible to find a long term edge.