Switch to the Gradient Tool with Ctrl and F1, then click and drag a line over the rectangle from the upper left to the lower right of the shape, re-directing the gradient to be a diagonal fill on what will be our sticky notepad's top page.
Copy (Ctrl and C) and Paste in Place (Ctrl, Alt and V) to create a copy of our rectangle exactly in line with, and on top of, our original.
Instead, send this first copy to the back of the drawing by pressing End or using Object -- Lower to Bottom, then nudge it to the left and down slightly by pressing the left arrow and the down arrow once each on the keyboard.
Now Paste in Place to create a second copy in the original position, and repeat the above process, this time with two keyboard presses instead of one.
Push these segments inwards slightly until you get this outcome: Let's get that gradient from the start onto this shape again, then.
On the Fill and Stroke panel, choose it from the bottom of the Linear Gradients dropdown box, and use the Gradient Tool once again to drag a fill from the tip of the curl to the larger side so that the darker edge is towards the lower right of the curled edge.
Revert to the Gradient tool, then click and drag a gradient in the opposite diagonal to before: bottom-right to top-left.
With this duplicate shape still selected, copy it to the clipboard but don't paste yet.
In the Fill and Stroke panel (Ctrl, Shift and F to bring it up), set the fill colour to R = 243, G = 249, B = 93.Press the 'Home' key to make sure this is above all your other shapes on the page.Keep this line selected and, holding down the Shift key, click on the page underneath it so you've got two objects highlighted with a dashed outline.Finally, Copy and Paste in Place this corner piece.Change the fill to R = 60, G = 60, B = 60, and on the Fill and Stroke panel reduce the opacity slider to about 35%. Finally, press Page Down or select Object -- Lower from the menus to send this behind the corner piece but above the rest of the drawing.