Step by step:
Day 1:
*Ally Serbia
*Spam gallies
*Convert ruler to general and use him
*Start transporting troops to Albania
Day 2/3/4 (doesn't matter)
*Declare war on Albania. IF Serbia doesn't reach Albania before Ottomans, restart. This will probably have to be done for 30 times before Serbia get the siege. Ottomans will reach it before but they will split their armies while sieging so Serbia will get the control. IF Serbia doesn't chose to stand still at their own lands.
If Ottomans doesn't ally Algiers, you could block Ottomans with just 24~ ships, and get an admiral for pete sake.
Once you block them, get get access through Moldavia/Poland and it's over, all your work for nothing.
GG latest patch
However, my most recent Ironman was quite good until I screw it up, which I can't really understand, but here goes:
*Allied stronk nations. Poland in the beginning, then Austria and finally Muscovy. Ottomans didn't declare war on me once (date was 1511).
I got all of the islands that belonged to me, and Trebizond.
2 Military techs above Ottomans (I had 10, so new troops) and they had 8. No military ideas or anything. I'm defending every battle (30k v 35k) and I still lost.
After that I just rage quit
I find playing Byzantium kinda frustrating