Freeze and flatten is what I do.
When I first started using a hardware synth in Ableton, I thought I had to route my sound to a separate audio track and record while the MIDI programming played the instrument. Then I discovered that freeze/flatten does that automatically. When finished, it converts your MIDI track into an audio track of your synth playing whatever patch you currently have set up.
One word of warning though... if you want to keep your MIDI programming for some later use, make a copy of the MIDI clip and paste it to another track or drag and drop it in your user library.
And don't leave any other MIDI clips in that track either. Once the flatten is done, all the other clips in that track will be lost. Ctrl+Z (undo) will back you out of it, in case of disaster.