External Memory without BGA?

I'm guessing that if you don't use the built in hardware memory controller you will end up using lots of scarce FPGA resources in your relatively small MAX 10. I'd suggest copying exactly the layout of the DDR lines from a dev board and using a BGA based memory device(s). If you are soldering it yourself, I'd suggest getting a BGA soldering practice kit and some paste and heat gun and working with it before doing your FPGA board. Essentially, you bake the board before use to drive off water, then put down a dot of solder paste on each pad on the board, carefully position the BGA and use the heat gun. There are plenty of tutorials on YouTube to show you how.