First of all, in a crosswind landing, you're supposed to land with one wheel first... depending on the strength and direction of the wind, its entirely possible this will result in you touching one main, then the nosewheel, and then the other main wheel. This is very disconcerting the first few times, but then you get used to it.
For the flare, you might find it helpful to visualise flying the main wheels down to the runway, making sure to keep the nose wheel out of the way until later. From your post, it didnt sound like you have a problem actually doing the flare, more of a problem in remembering that you have to flare.
Ask your instructor to remind you to flare, every time you land, for about two weeks. From then on, they can remain quiet, but in your head, you will still hear their voice saying "flare", and you will remember to flare.
Also get your instructor to demonstrate some one-wing-down crosswind landings. In heavy jets, you will have to crab, instead, but in a lighty, putting a wing down is by far the easiest way, because there is no need to worry about performing a dance with the controls to straighten up and level your wings while you're half a foot off the runway. Just go ahead and land one wheel first.
Even in a low-wing aircraft, you will not clip the wingtip on the ground. There is plenty of room.