I do a mixture of samples and own beats. Generally start with something simple either 4 to the floor kick or a drum pattern I've laid down to start a track.
Or I may have a sample loop that appeals and use that initially, build my own beats around it and as mentioned do some eq'ing and filtering to the sampled beat. This maintains the groove/vibe.
Might actually remove the sampled loop evetually as my own beats have overgrown the original sample.
My mindset in general is if I am making a track I want a clear concience and try not to use other peoples works and don't use warez. Good honest tracks for me is more productive.
Dont get me wrong nothing wrong with sampling as long as you are creative and clever. AS you mentioned splicing sampled, glitching them, processing with effects etc can get some great results. By doing that I don't feel like cheating. Bit like painiting copy a picture and you haven't originated. Copy the genre and create your own pattern and colour...you have your own sound and original production.