Building what we call a table saw with tilt and elevation would be fairly serious engineering, not impossible. You could Google a parts diagram to establish the reverse-design process. Otherwise, there are many blank tables made that accept a hand held circular saw readily. Far less intensive project you could do as we say 'at the kitchen table'. They are little but a table with enough clearance underneath to mount a functioning saw package by it's bed plate. Commercially, I'm sure they have a secondary switch or wire out that in handle so it runs independently of being gripped.
While self built tools are a great goal, sometimes you have to spend cash on 'the real thing' to get started. Unless you're after a 1950's Unisaw, Oliver, Moak, Crescent, Rockwell...a craftsman can build his own. Grand old iron cannot be duplicated without vast resources.
I don't know where you are, but we call it $$$.$$, others €€€.€€.