built-in means inner of something, You placed or fixed some properties or factors inside equipments or sets in advance. for example, the car can move automaticlly by buit-in sensors. Thus, the sentence means you can easily produce productions alike in some properties by using a template.

If something is 'built-in' it has been included in the original design and construction, and not added later. For example, 'New houses have things built-in to help reduce their impact on the environment that older houses do not have.' 'Consistency' is the quality of being reliable, predictable, stable, etc... So in your example the template is designed to be part of the process so that it creates results which are the same.