There are seeds on JM now. Drive around and look for trees in the landscapes of better class commercial buildings and cemeteries. The seeds that are down at the base of the tree now are probably more mature than those still on the tree. They mature and fall over a month or six week period so you can haunt them on non-business days like Sundays and get all you can stand. Often, there are really good years for seeds/fruits followed by off years with little or none, so don't be bewildered if you bump into a bad year. You can buy aluminum roasting pans from the Dollar store, ~12" x 18" x 4" that you can punch drain holes in the bottom with a nail and fill with dirt. Broadcast the seeds on top and cover with 1/2" crushed leaves and set in partial sun on the ground. In spring you will be rewarded.
Seedlings are tasty, so any protection from birds and mice will be helpful.