I use the word easy based on the fact that if you have successfully built a spaceship the next steps should be a doddle. If you’ve never even built an IKEA bookcase then you may need another adjective.
First out of the blocks we could simply use another force in place of gravity. Electromagnetism is an easy force to generate with electricity but of course we are neither electrically charged nor magnetic. So we need to add magnetic material to ourselves, metal soles on our shoes would certainly stick us to the floor but the rest of our body would still be weightless with the undesirable affects and inconveniences that entails, muscle and bone waning for example. We could wear a bodysuit made of a magnetic material. This would apply a force over our whole body pulling us down to the floor although a flexible magnetic material doesn’t come to mind but I’m sure it’s not beyond the realms of possibility. This would certainly help prevent the decay of our body in a weightless environment and would help with activities like sleeping. It would not however apply a force to anything outside the suit or to our internal organs etc. So issues such as relieving one’s self and terrible acid reflux would not be aided in anyway. Moreover all of the other objects would still be floating about the place. We could add a magnetic plate to each of these but quite how you could make a glass of water magnetic is beyond me. Magnetism is promising then but doesn’t hold all the answers.
Luckily science provides us with a closer alternative, an identical alternative in fact. Einstein realised that the effects of gravity are identical to those of acceleration, they are in fact equivalent. Picture how you are pushed back in your seat when you accelerate quickly in your car. Gravity on Earth is equivalent to experiencing an acceleration of 9.8 meters per second per second or if you prefer accelerating from 0-60 mph in 2.7 seconds. Therefore if our spaceship accelerated at 9.8 m/s/s we would be pulled to the back of the space ship in an entirely equivalent way to how we are pulled onto the surface of the Earth by gravity. More than this, unlike the electromagnetism idea, everything would be pulled to the back of the spaceship and so we could live quite happily there.
The issues with this are the following, we would have to accelerate for the entire duration of our journey which means by the end of a journey of a few years, which is the shortest we could hope an interstellar trip to take, we would be travelling incredibly fast and so slowing down at our destination would either be painful or very slow. If we began to decelerate at 9.8 m/s/s at half way then we could have gravity for the whole trip but it would flip upside down half way through and I think we can agree you would not be best pleased if the gravity in your living room suddenly pulled everything to the ceiling. Secondly, we would be travelling quite slowly at the start and end so clearly this is not the fastest way to get to a destination.
Luckily there is a solution, circular motion. Everyone who has been to a playground knows that is you sit on a roundabout as it’s spinning we feel a force trying to throw us outwards from the centre, this is a reactionary acceleration towards the edge of the circle. In much the same way, we could build a space ship that consisted of a large spinning tube which, if spinning at the correct speed, would ground us to the inner surface of the tube in an identical way to gravity; much like a giant hamster wheel. This has all the benefits or the previous idea but without the problem of the direction of our gravity changing mid-trip. Even better, we could then move at any constant speed we like for the duration of the trip. This then surely is the solution. Of course the disk would have to be very big for the inevitable curved surface we would be living on to be practical, it would have to be more of a flying city than a spaceship for it to be big enough to be practical. This is then a solution for colonisation missions but perhaps not for small manned missions. But a shorter, smaller mission is more likely to be able to cope without gravity.
In truth, the real, more practical solution undoubtedly lies in a technology as of yet undiscovered. Doesn’t it always.