Firstly you need to find a place known for producing big perch and spend your time there. In Alberta, Slave Lake is probably top of the list as it offers the space and food resources to grow numbers of big perch. Yes big perch are found in smaller bodies of water but more numbers of big perch are found in bigger watersheds.
Secondly, big perch tend to hang around different areas than small perch, not sure if as they get bigger they tend to hunt different food resources but generally if you are catching bunches of small perch, the giants might be elsewhere.
Our best luck has always been away from community holes and crowds, if looking for new water, I start looking on sand flats 6-12 feet of water near a creek/river mouth.
Also most fish are caught actively jigging. I tend to use small jigging Rapalas and Northland Puppet minnows. Now here is my trick. I don't tip the lure with any bait just plain. I find any attached bait kills the swimming action but I do chum the hole with bits and pieces of minnow during the day.
Plan to be quiet in shallow water and being in a dark hut with clear water can help spot giants that are nearby. Of course cameras work well for this also.
I have been fortunate to see multiple perch stretch the tape to 16 inches and beyond but this was in another province. Still hunting for yellow monsters in Alberta. This winter will see some dedicated time in pursuit of jaw droppers and I will post any results. Let me know if anyone wants to join the hunt.