Following on from Brett, it’s actually a little more complicated
Even if you are doing small lots (2 or 3) a stencil can be a real life-saver.
You can relatively easily dab solder paste from a syringe to do 0603 and SOIC style parts. Once you get to complicated land patterns (pushbuttons, connectors) or fine-pitch (e.g. the 0.6mm pitch on the STMF32 parts or FPC connectors) a solder stencil gives much better results during reflow.
I guess the short takeaway is smaller parts require more accurate paste volumes.
I just use masking tape to set up a stencil for short runs (<10 boards). There’s a load of youtube tutorials for this.
( I should also add, using a stencil is very rewarding, you can feel like a ‘real’ board producer)