Having taken many female rectal temperatures, my preference is to start them laying on their backs, undo their belt, buttons and unzip the front giving a peek at their “ unmentionables “.
If it’s a skirt I had them remove it, ( obviously )
place it or hang it so it wouldn’t get wrinkled. Then I had them get on the table, face down and proceed as described below. Skirt-no reason to have them start on their back.
Then have them roll onto their stomach. I have them lift their hips, and I lower the jeans or pants ( that includes shorts) , the jeans/ slacks/shorts brought down behind the knees. I have them stay slightly arched as I lower their undergarment ( sometimes in that position I had to lower their pantyhose too. ) which wind up about mid thigh and the legs spread ( sometimes the pants, jeans, shorts, pantyhose are removed completely to facilitate spreading of the legs. ) if they prefer and it’s their choice to keep their legs closed, no need to remove any garment (s).
Next I let them return to laying on their tummies giving them a few moments to compose and calm down ( some were anxious)*while I get the thermometer, lubricant and needed accessories for the temperature taking.
*if they changed their mind saying they did not want their temperature taken, I stopped and did not take it.