Select the inside-arc at left side of sketch and apply radius constraint with radius 7.5 mm.
Select 2 lines that makes a corner at left side of sketch and apply perpendicular constraint.
Then select 2 straight lines extending from both ends of the inside-arc and apply parallel constraint.
We will adjust depth and thickness of the tablet holder. Select each line and apply length constraint with 5 mm.
We will adjust foot position at right side of sketch. Select a point on the foot and the horizontal axis of the sketch plane, then apply Point on Object constraint.
Select inside-arc at right side of the sketch and apply radius constraint with 5 mm. Then select a straight line of the foot and apply horizontal distance constraint with 20 mm.