Goa'uld heavy industry.
How do the goa'uld maintain their industrial base if they are ruling over primitive worlds and intentionally keep their subjects, even the Jaffa primitive? The key is a system of technological enslavement that involves a divide and conquer strategy. The Goa'uld worlds are divided into two classes.
Resource rich Source worlds. These provide food, slaves, hosts and mined resources some pre-processing is done on Source worlds but they are intentionally kept primitive. Resources are gathered either by raiding them or by demanding tribute of raw resources or processed items to be delivered to the goa'uld lord or a Jaffa Representative. Resources far from the gate are gathered by a Al'Kesh or Teltak ship and relayed to a larger ship or to the gate.
One kind of refined resource produced are Iconbars. These are metal ingots or rods made to exacting specifications by thousands of smiths on many low technology worlds. The bars are covered in complex pattern of dove tailed pegs. These interlock but there is no way to slide the dovetails together. The Goa'uld have a devices, Originally from Ma'chellos world, that teleports these rods together producing a very strong solid structural elements. These are the key to constructing Goa'uld ships and large buildings. Once interlocked the rods can't be moved in any direction. However because it is a composite of Iconbars, any attack is resisted because cracks will not propagate through the block or girder.
The flying hoversleads used by some Goa'uld can also be used for regional transport. These are slow and hover only a few meters from the ground but they can carry a cargo of up to a ton. One was used to transport the sarcophagus containing Skaara as a host of the Goa'uld Klorel. Within the Serpent's Grasp. End of season 1. Up to six hoversleads can be linked to a pilot pod about the same size to create a reliable gate capable vehicle that can travel great distances from the gate over open land and water. Ra was one of the few Goa'uld lords that refuses to use this craft for reginal transport because, if captured, they make rebellion easier.
The other type of Goa'uld world is a foundry world. Tollana became such a world after its capture. All agriculture is banned on pain of death making the population dependant on the Goa'uld Lord for food. The technology and literacy is kept high. The population is employed to make advanced technology. Those not useful for this purpose are taken to other worlds to work and are used as hosts.
Foundry worlds are often equipped with systems of advanced transport. The most advanced is a net work of ring transporters. Some are on a small fleet of orbiting modified Tel'tak. These can pick up cargo in one place and beam it down instantly to another location. Foundry worlds only make parts. They are never used to craft a final assembled device. Goa'uld lords with more than one foundry will distribute tasks across them to keep the foundry world population from understanding or copying and using the technology they make.
The average Jaffa can assemble and clean his equipment but must rely on the Goa'uld to supply the parts. As the war between various Goa'uld factions raged; some Forge worlds were isolated resulting in famine. It also resulted in distributed tasks being disrupted further weakening the loosing lords power and enhancing the victors industrial power.
This is done on ships or on Source worlds. Parts are imported by the gate or by a ship. Slaves from both types of worlds are used. These slaves are chosen for their religious loyalty and obedience. They never return home. A few junior Goa'uld are used to do the final instillation of critical systems and electronics. A large project like ship assembly may be done on a source world near the gate. The construction of smaller ships: Al'Kesh, Tel'tak and death gliders is generally done on a much larger ship such as a Ha'tac. Smaller items are assembled on smaller ships or in workshops on larger ships.
However the Jaffa rebellion was possible because some Jaffa became familiar with the pattern of industrial feudalism employed by their Gods. With the defeat of the Goa'uld many former forge worlds are either rediscovering agriculture and importing all manner of seeds and livestock or have been depopulation via the gate creating millions of refugees.