Gesso panels for oil painting - plus how to make your own

Gesso covered hardboard - sometimes know as Masonite - smooth surface on one side rough on the other
By varying the application of the Gesso different surface textures can be used but use with a degree of caution as the texture can fight with the painting. The opposite is to sand it smooth therefore making it ideal for detailed work. 

Hardboard/Masonite is a manufactured product made from wood.  Wood chips are blasted with steam into long fibres and formed into boards, which are then pressed and heated to form a finished product. 
For oil painting hardboard/masonite can be primed with acrylic gesso or canvas can be glued on top of it. One thing to keep in mind however is that large boards have tendency to bend and therefore for larger paintings extra backing support would be well advised as well as painting the back of the board.

The Untempered variety is used widely by artists and thought safer, than Tempered, for archival painting although it is less durable at the edges as it has loose fibre content. By preparing your own surfaces (canvas or hardboard) you can choose any dimensions or shapes you like and many artists do prepare of their own.

Primers really control the texture, absorbency of the support, while colour can also be considered. Priming hardboard for oil painting is inexpensive when compared to other supports, the boards can be purchased quite cheaply, although these will need a number of coats of acrylic gesso (3 to 5 coats) before painting (on the smooth side which has been lightly sanded), so takes more time but a number can be produced at one time.

As an alternative to making your own, a number of companies now make readymade versions but to set sizes usually the same sizes as for canvas boards.

Making Gesso covered boards:
I purchase full sheets of hardboard or masonite (depending on location and supplier) and then cut to the required sizes. Depending on the size needed - a division of the width and/or length results in little or no waste.

After cutting, sand the smooth surface and edges.

I use Winsor & Newton Artists Acrylic White Gesso. 

Each board will have five coats applied to them with a large household paint brush - used only for gesso. It's better to use one with long hair as the gesso does dry quickly. Therefore it's best to keep the gesso away from the ferrule and wash the brush as soon as you have finished. Allow each coat to dry before adding the next. Larger boards can warp, if this happens' paint the back with a coat and if very big a support frame will be needed.

If you want a smooth surface, sand the surface between each coat.

For slight uneven texture, use straight from the pot and retain some of the brush marks. Vary brush pattern for each layer.

For a fine canvas like texture, brush horizontal for one coat, then vertical for the next, repeat horizontal then vertical until all layers have been applied.

For more texture, add some texture paste to second or third layer but beware that the texture itself doesn't compete with the brush work of the finished painting.