Pizza oven floor options

[Roosterrex]

Have made a temporary pizza oven (just getting started)the oven floor is red bricks but they are a bit uneven what materials could I use to sit on top of the bricks to make it smoother

[JRPizza]

Most folks are going to tell you that red bricks are a poor choice for the floor as they will not hold up well with the heat of the direct fire. What early stage are you in?
If you accept the risk of the bricks breaking down and spalling, and they are not mortared down, I'd recommend pulling them up and using a leveling mixture (sand, fireclay, etc) underneath. If they were firebrick many folks knock down any slight irregularities but making the surface level is the best approach, and with standard red brick grinding on them isn't going to make the surface any more durable.