No supplement will 'block carbs'. That is total marketing BS. Think about it. If your body wasn't able to absorb the food you eat, you would very quickly develop a nutrient deficiency.
What you can do (and what N2slin does) is increases muscle insulin sensitivity so the carbs you eat are shuttled towards muscle cells and away from fat cells.
Fish oil, apple cider vinegar and cinnamon are three natural foods shown to increase muscle insulin sensitivity. If you don't want to use N2slin. Those 3 are going to be your best bet for naturally increasing muscle insulin sensitivity.