If I wanted to start recording a macro using command-line mode, how would I do this?
Additionally, if I wanted to bind this action to a key, how would I do that in my .vimrc?
For the first question
:normal! qa
That would start recording a macro to the "a" register. You may change that to any lower case letter.
To map F3 to it, for example, you could use
noremap <F3> :normal! qz<CR>
