3 inch copper drain no flange

First time bathroom remodeler here. After installing my new floor I proceed to install the toilet. Unfortunately I noticed that there was no flange. I have a 3 inch copper pipe with no flange. The toilet was previous installed with only a wax gasket and a super ring.

Do I put it back this way or should I install a flange? If I install a flange I have no access from below, can I solder from above?

copper

Yes you need a flange, and the best way is to solder it from above.

Thanks.

If you don't mind I just want to clarify "from above." This does mean that I would be soldering the inside of the flange where the flange and pipe meet. I just want to make sure I fully understand before I tackle the job. Thanks for your help.

flange

Yes, but it would not be that plastic or steel flange you show in the photo. It would be a brass one and it would slide over the pipe. You would heat the joint from the inside of the copper riser.