Butt one side up to the wall, scribe the other side and cut with a coping saw/adjust with files - it's fiddly but easier to adjust than 45 degree angles on both sides (especially as your corner probably isn't exactly 90 degrees). Filler will solve the final fit!
Butt one side up to the wall, scribe the other side and cut with a coping saw/adjust with files - it's fiddly but easier to adjust than 45 degree angles on both sides (especially as your corner probably isn't exactly 90 degrees). Filler will solve the final fit!