This is a very common base that is used in a ton of origami models, especially when making birds.
1) Start off with a square base.
2) Make two valley folds along the black lines
3) The completed valley folds. Crease the folds well and unfold them.
4) Now make another valley fold across the top along the line. You’re going be to making a Petal Fold.
5) The completed valley fold. Crease this fold well and then unfold it.
6) Now lift up the top flap and fold it back across the crease you just made near the top.
7) As you raise the flap up fold the edges along the creases you made in step 2.
8) This is the end result. Most of the folds should fall in place because of the creases you made earlier.
9) Turn the paper over and repeat steps 2 to 8 on the other side. This is the completed bird base.
If you open the paper up you’ll see the following moutain (black) and valley (red) folds.