Here are some low carb alternatives to common ingredients that you may use when you bake your desserts:
Flours: choose coconut and nut flours. One of the best is almond flour because it is very versatile for most dessert recipes and because of its low carb content. You can also choose soy, seed and bean flours.
Sugar: instead of white processed sugar, choose stevia. It is a popular plant-based sugar substitute. It is naturally sweet and contains no carbs at all. The price may be steep so you can consider sugar alcohols like your xylitol and mannitols. Artificial sweeteners such as aspartame, saccharine, and similar compounds are also options.
Butter and oils: purees can be a substitute, pumpkin purees are popular, but you can also use other bases such as other fruits.
Unsweetened versions of your baking ingredients are always a good choice. For example, if cocoa powder is called for in the recipe, then choose an unsweetened version.