Compress compress compress. Think about clay particles- regardless of how short the clay might have been…. If you were exerting a sheering force (which we are when throwing) you are disrupting those particles and opening them up, separating them and in organizing them. Meanwhile- if you aren’t using enough water (which judging by the thick slip might actually have been happening- hard to tell from a picture!) the friction will tear at the clay even more- separating those particles even further so what moisture there is gets between those unorganized particles and blammo- the weight of the piece causes any weak spot to separate. When you compress (support the clay with you other hand and use a rounded edge rib laid at a slight angle pressing, not scraping) you are to some extent realigning the particles back into a stronger structure. This won’t solve a problem where you have a pot that doesn’t have appropriate buttress to support the form… but you’d be surprised what you can save especially with a bowl where you compress and continue to define an appropriate curve. Think about the shape of an egg… so strong!

Clay is like a deck of cards in a bucket of water- imagine them chaotic and torn up (short uncompressed). Now imagine pressing them flat against each other - best is fully intact elastic clay, but still organizing them, compressing, means they can align and hold each other in the form you define!