To create a specific size shape in Canva, follow these steps:
Create a new project or open an existing one.
Click on the "Elements" tab in the left panel.
Choose a rectangle shape from the available options.
Drag the rectangle onto your canvas.
Select the shape, then click on the "Lock aspect ratio" button in the top toolbar to unlock it.
Enter the desired width and height in the respective boxes in the toolbar.
Now you have a custom-sized rectangle in Canva.