It sounds like you don't have a jointer, so I suppose the next best thing would be a router table. If that's the case, make sure you have as little gap as possible, and where the bit comes up through the table close that up also. Use a push stick, route one side, and then true it up on the table saw if you have one.
If you have a table saw, get some two sided tape, and tape your wood to the edge of a straight board. Run it through the saw. Do that for all pieces. When done, set the fence up for the size you need and put the trued side up against it, make your cut, then rotate it to the next edge and repeat until all sides are straight.
Better yet, make yourself a "Poor Man's Jointer". That is a piece of wood that has been cut leaving a dog leg at one end. You would use this dog leg thing as a stop to endex your small piece so you can push the wood through safely. Do one side only with the PMJ, and finish by the instruction from the above paragraph..
If you choose to do it this way, thank me after you're done if you don't get hurt….... ......... Jerry (in Tucson)
If you have a table saw, get some two sided tape, and tape your wood to the edge of a straight board. Run it through the saw. Do that for all pieces. When done, set the fence up for the size you need and put the trued side up against it, make your cut, then rotate it to the next edge and repeat until all sides are straight.
Better yet, make yourself a "Poor Man's Jointer". That is a piece of wood that has been cut leaving a dog leg at one end. You would use this dog leg thing as a stop to endex your small piece so you can push the wood through safely. Do one side only with the PMJ, and finish by the instruction from the above paragraph..
If you choose to do it this way, thank me after you're done if you don't get hurt….... ......... Jerry (in Tucson)