This is a question that cropped up just this week, many beginners are confused about drawing boards, are they necessary? Well they do have their advantages for drawing. The drawing board is a support that allows you to draw at an upright angle which is better than drawing flat on a table or desk. The reason is because you can draw without having to keep looking up from your drawing.
When you are measuring with a pencil the measurements are more accurate once transferred to the paper as you are not distorting the angle when your paper is upright or more upright. It helps if you can see your subject over the board so you are not stretching your head over the board, so I position my board at an angle that is comfortable for seeing over the top. I like to prop my drawing board against a desk or another chair in front.
Where Do you Buy Drawing Boards?
Any flat board will do, but you can buy specially made drawing boards in art stores. I got my piece of fibreboard from a DIY store many years ago and have been using it ever since. If you are purchasing a piece of wood, a good bit of advice is that some wood can be very heavy and it can became uncomfortable have it propped up on your knees due to the weight. You don’t want a flimpsy piece of wood that warps either, I found a 1.25cm (half an inch) thickness was fine.
If you decide to purchase a drawing board it is not a bad choice because they are specifically made for artists. Many have a mechanism so you can choose the angle you can have your board at (as in the image).
The size will depend on the size paper you like to draw with, you need a board slighter bigger than the paper size. I use a piece of fibreboard that is just bigger than A3. Chipboard is cheap but quite rough and normal hardboard is too thin. I use masking tape to fix my paper to the board, you can also use metal clips.
Be careful to consider the size you need as they come in different sizes, a small board would be more portable but if you work large you might need something larger.