Im an amateur like yourself. This has helped me in the past. Clamp a bit of timber taller than it is wide flush to your cutting line. 4x2 for example. Make sure it's square!
Take a sharp chisel and bevel out. ie. flat side toward your non cut side, give it a little bit of a tap.Turn your chisel over and gently pare away the waste side. easy now. Just a touch. Now you have your notch. Draw your saw a few times keeping the body against the clamped timber. Pay attention to keeping your body and feet in alignment with the most easy stroke. Relax, measure your breaths and take your time. Let the weight of the saw do the work, never force it. Extend your fore or index finger along the axis of the saw, draw the saw. relax! keep going. nearly there! support the work when you're nearly through.
Now practice 600 times.
You're the target of my first ever woodworking advice lol.
Sometimes there's no shortcuts. You gotta learn how to do it by doing it.
(still learning here if thats any comfort)
cheers
Chris