Picture placeholder with rounded corner bottom left/right in PPT 2019

Go to View - Slide master and click on Insert layout. Now click Insert Placeholder and choose Picture.

Drag the + until you obtain the perfect dimensions and release the mouse button.

This is the result:

Select the placeholder and click the Shapes format tab, in the Insert shapes group choose Edit shape and then Change shape, select the rectangle shape. Nothing will change at first sight but this step is necessary to be able to change the shape of the placeholder. If you do not take this step you will see that the options will stay greyed.

Right-click the border of the placeholder and choose Edit points.

Right-click the border of the placeholder where you want the curve to start. Then choose Add point.

Now click on the point in the bottom left corner of the shape and drag to your right.

Use the handles to get a perfect rounded corner.