Normally this would entail pulling out the USBTiny programmer and wiring up the necessary 6 pins. Being in a hurry - I tried to get a Digispark board working... These are neat little ATTiny 85 boards (they also do a 'pro' with a 'beefier' tiny - a 167 I think) This was ideal for my needs - it has an onboard voltage regulator (and I wanted to power LEDs). However I wanted as small (read flat) a form factor as possible - for a wearable - and I didn't want to solder on pins..
So - the board has a bootloader and can be programmed via USB.
Can it be done via Flowcode - yes

First download the micronucleus program from https://github.com/micronucleus/micronucleus/releases
Unzip the file and you'll need the command_line program x86_64MINGW micronucleus.exe
Note you might need to install a USB driver (see the digispark board at http://digistump.com/wiki/digispark) for instructions on setup.
Note that there are many 'clone' boards - and the one I have has version 2.2 firmware (and wouldn't work from Arduino IDE which was expecting v1.6) - There are newer (and smaller) versions of the bootloader - I might experiment with later.
Then I created a very simple batch file
Note that the address you unzip the exe file to might be different... Adjust line 3 to suit...@SET Programmer=micronucleus
D:\micronucleus\commandline\builds\x86_64-mingw32\micronucleus.exe %5
@ECHO.
@ECHO Programming successful!
@EXIT 0
Then I saved this to C:\Program Files (x86)\Flowcode\Common\Compilers\avr\batchfiles
Then pointed FC to use this from Compile Options - Programmer Which I saved as 'Micronucleus'
Then I can compile ATTiny85 code and upload it quickly and easily from within Flowcode. When the 'programmer' runs I just need to plug the board into a USB port...
Did I manage it in time - no

Martin