That's the only way I do it. Is open bucket fermentation. As long as your must and equipment are sterile. Everything will be okay. There is enough co2 created to create a barrier for protection. You will want to rack it into your carboy when the gravity is around 1.040 to 1.030 and place your airlock. I have yet to have any issues with this method.
I'm embarrassed to admit this.. most people use a towel to cover the bucket while fermenting this way before transfer. This is to help with vinegar flies and anything else that could land in it. I actually use pantyhose to cover the top of the bucket.
Oxygen at initial fermentation can actually benefit yeast production.